WordNet sense 1 (a ridge of land that separates two adjacent river systems):

watershed, water parting

WordNet sense 2 (act as a barrier between; stand between):

separate, separate

WordNet sense 3 (separate into parts or portions):

dissever, split, carve up, split up

WordNet sense 4 (come apart):

part

WordNet sense 5 (force, take, or pull apart):

disunite

WordNet sense 6 (perform a division):

fraction