Arrancars (破面(アランカル) arankaru?, Japanese for "broken mask," Spanish for "to tear off") are the most humanoid Hollows, having their masks almost completely removed—and from this—they gain the powers of a Soul Reaper, including a zanpakutō, as well as strength, speed, and intelligence beyond the level of normal Hollows.
In addition to those improvements, Arrancars also have hierro (鋼皮 (イエロ) iero?, Japanese for "steel skin," Spanish for "iron"), skin hard enough for them to fight against sword-wielding opponents bare-handed, but can still be cut through. Arrancars use a technique known as sonido (響転(ソニード) sonīdo?, Japanese for "transfer effects," Spanish for "sound") to travel at extremely high speeds across a short distance. Stronger Arrancars have been shown to possess proportionally harder hierro or faster sonido, among other abilities, either unique or based on common techniques, such as the several variants of the cero technique.
Like Soul Reapers, all Arrancars possess a zanpakutō (斬魄刀?, lit. "soul-cutting sword"). Unlike a Soul Reaper's, however, whose zanpakutō is a manifestation of its owner's soul, an Arrancar's zanpakutō manifests his or her power as a normal Hollow. With occasional exceptions, an Arrancar's zanpakutō resembles a regular sword in its "sealed state." When "released" through a process called resurrección (帰刃(レスレクシオン) resurekushion?, Japanese for "returning blade," Spanish for "resurrection"), the sword combines with and changes the appearance of the Arrancar. Part of the Arrancar's origional Hollow form is restored, and the Arrancar is granted greater strength and access to his or her original abilities from resurrección. In some cases, Arrancars can discard or remove certain elements of their released forms to better focus their powers. This results, however, in the Arrancars losing those attributes permanently, like ripping off one's own limb.
Arrancars become major antagonists in Bleach during the second part of the series, as they are led by Sōsuke Aizen, who uses the Hōgyoku to create and perfect the Arrancars. According to Tite Kubo, many of the Arrancars are named after real life architects and designers