WordNet sense 1 (the time of the last part of something):

fag end, tail end

WordNet sense 2 (a spy employed to follow someone and report their movements):

shadow, shadower

WordNet sense 3 (the fleshy part of the human body that you sit on):

backside, behind, bottom, bum, buns, buttocks, can, derriere, fanny, hindquarters, posterior, rear, rump, seat, stern, tush, arse, fundament, keister, nates, prat, tooshie, tush, hind end

WordNet sense 4 (the rear part of an aircraft):

empennage, tail assembly

WordNet sense 5 (the rear part of a ship):

poop, quarter, after part

WordNet sense 6 (go after with the intent to catch):

chase, dog, tag, track, trail, go after, give chase, chase after

WordNet sense 7 (remove or shorten the tail of an animal):

bob, dock