WordNet sense 1 (the region of the angle formed by the junction of two branches):

crotch

WordNet sense 2 (lift with a pitchfork):

pitchfork

WordNet sense 3 (the act of branching out or dividing into branches):

ramification, branching, forking

WordNet sense 4 (divide into two or more branches so as to form a fork):

branch, ramify, separate, furcate, separate