WordNet sense 1 (put an end to a state or an activity):

cease, discontinue, quit, stop, lay off

WordNet sense 2 (allow the other (baseball) team to score):

allow

WordNet sense 3 (leave (a job, post, or position) voluntarily):

renounce, resign, vacate, resign

WordNet sense 4 (give up what is not strictly needed):

spare, dispense with, part with

WordNet sense 5 (part with a possession or right):

free, release, relinquish, release

WordNet sense 6 (lose or lose the right to by some error, offense, or crime):

forfeit, forgo, waive, throw overboard

WordNet sense 7 (relinquish possession or control over):

cede, deliver, surrender

WordNet sense 8 (give up with the intent of never claiming again):

abandon

WordNet sense 9 (give up in the face of defeat of lacking hope; admit defeat):

drop out, throw in, chuck up the sponge, drop by the wayside, fall by the wayside, throw in the towel