"Allows your Explorer to quickly train a small ambush party of Blowgun Warriors."—In-game description
Carib Ambush Party is a technology in Age of Empires III that can be researched at a Trading Post built on a Carib settlement once the Colonial Age is reached. Once researched, it allows hero units to train up to 12 Carib Ambushers, which are statistically identical to Carib Blowgunners but are trained twice as fast.
Note that Asian civilizations who can have two Monks at the same time cannot train two Ambusher armies, as they both share the train limit of 12.