(verb: BRAY-kee-ayt, BRAK-ee-ayt, adjective: BRAY-kee-it, BRAK-ee-it) 
verb intr.: To move by swinging from one hold to another by using arms.
adjective: Having arms.
Etymology
From Latin brachiatus (having arms), from brachium (arm), from Greek brakhion (upper arm). Ultimately from the Indo-European root mregh-u- (short) that is also the source of brief, abbreviate, abridge, brassiere, and brumal brumal. ]
A gibbon brachiating:

[Photo: Jeff L. Milsteen www.flickr.com/photos/20973954@N07/2603222061 ]
Usage
"Thick-furred, with a red face, the monkey moves by sprawling out and brachiating from branch to branch through the high forest canopy." — Roger Rosenblatt; Earth's Green Gown; Time (New York); Jun 17, 2004.
"The new superfriends head out on their first missions: the isotope feint and a related museum heist, which allows Sydney to dress in cat-burglar clothes and brachiate around an unguarded exhibition." — Virginia Heffernan; Yet More of One Face in Season 4 of 'Alias'; The New York Times; Jan 5, 2005.