Nnoitra is the tallest Espada, excluding Yammy Llargo (whose height varies under certain circumstances), dwarfing even Chad by half a foot. This fact is emphasized by his very thin and lanky body. His face is frequently set in a huge smile which reveals his upper teeth, similar to Shinji Hirako. His black hair hangs past his shoulders, concealing the left side of his face and a large white eyepatch with one exposed dark gray eye. The eyepatch hides his mask fragments, consisting of a small set of jawbones and teeth surrounding his Hollow hole. The tattoo signifying his rank as 5th Espada is located on his tongue. His clothing consists of a modified Arrancar jacket with an overblown spoon-like hood and an opening starting at the neckline, showing most of his midsection, and closing at his waist. He wears the standard hakama but the ends of his pant legs close inside extended and curved boots. When he was the 8th Espada, Nnoitra's hair was shorter and messier, he lacked the spoon hood, and he wore his jacket's collar upturned.
Personality-wise, Nnoitra is extremely rude and lecherous, accented by his snake-like eyes and perverted attitude towards Orihime, rudely referring to her as "pet-sama". He even went as far to ask Ulquiorra Cifer how well he "disciplined" her. He is quite possibly the most foul-mouthed character in the series, even more so than Grimmjow. He is also a firm believer in male chauvinism and openly insults (and regularly attacked) the former 3rd Espada, though it's unknown if he holds the same grudge toward Tier Harribel. His overall goal is to prove himself to be the absolute strongest of the Espada, not wishing to waste his time killing those he dubs "weak". However, he has no qualms attacking stronger opponents who are already injured, a trait both Ichigo Kurosaki and Grimmjow Jaegerjaquez berate him for. He also loathes looking weak, and thus, will refuse all forms of assistance offered to him during an ongoing battle, as seen when he struck his lone Fracción, Tesra Lindocruz, for running over to his side (and releasing Orihime Inoue in the process) after Nnoitra was blasted by Nelliel's Cero Doble. He does, however, appear to have at least some amount of concern for his sole Fracción's well-being (unlike Grimmjow, who did not even mourn for his deceased companions), having attempted to warn Tesra to withdraw from battle after he determined via his Pesquisa that Kenpachi Zaraki was stronger than he had initially anticipated.
One of Nnoitra's most notable characteristics is his insatiable bloodlust and hunger for battle, which exceeds even Grimmjow's and is rivaled only by Kenpachi Zaraki's philosophy of literally living to fight time and again. Nnoitra's idea of a fulfilling end to his life would be to die on his own two feet while drowning on his own blood. Because fighting is his way of life, he continually strives to be stronger, and it is later revealed that he considers himself indebted to Aizen for allowing him to exceed his natural fighting limits. To appease his craving for a good fight, he even defies a direct order from Aizen to patiently lie in wait for Ichigo Kurosaki and his friends when they try to infiltrate Las Noches in a bid to free Orihime Inoue.
In his later moments during his battle with Kenpachi Zaraki, he begins to show signs of weakness and desperation, and becomes increasingly frustrated over his inability to overcome the powerful Captain. This stems from an inferiority complex he developed while serving as 8th Espada, due to his apparent inability to beat his opponents. Whenever his opponents refuse to kill him during a battle, particularly Kenpachi and Nelliel, Nnoitra takes it as a direct affront to his pride, because in his mind, neither Nelliel nor Kenpachi seem to think of him as their equal or superior. This shows a more honorable side of him as even he wishes to be treated as equally as every other opponent he has treated. Ironically, he treated virtually everyone of his opponents the same way, unfairly and through dishonorable methods. He also does not hesitate to use any means - even unfair ones - in order to prove his superiority in the battlefield.
(聖哭螳螂 (サンタ テレサ), Santa Teresa; a common Spanish language name for "Mantis religiosa," or in English, "Praying Mantis," Japanese for "Sacred Crying Mantis"): Nnoitra's Zanpakutō is uniquely different from the Zanpakutō of many of the other Espada since, unlike the basic sword shape of most Arrancar, Santa Teresa takes the form of a giant axe-like weapon bearing two crescent moon-shaped blades fused together at the backs, with a large looped chain connected to the shaft at the end of the handle. The chain is connected to Nnoitra's waist, allowing him to perform long-ranged attacks. During flashbacks to Nnoitra's time as the 8th Espada, it had only one crescent moon blade on his Zanpakutō, as opposed to the two that it features now.
The release command is Pray (祈れ, inore). Nnoitra gains an extra set of arms, which take on an insect-like carapace and clawed hands, with each hand holding a large scythe-like weapon as well. The scythes themselves resemble the appendages of a praying mantis, and have a small golden tassel at the end of each staff. He also gains a golden marking extending from his forehead to below his right eye, as well as a pair of horns on his head, his left horn longer than his right, resembling a crescent moon. His hollow mask also changes, becoming torn, with the teeth extending over the hole itself. The weapons are used by him to both defend and then rapidly attack his opponent, as is seen in his fight with Kenpachi.
Info from : http://bleach.wikia.com/