WordNet sense 1 (financial resources provided to make some project possible):

backing, funding, financial backing, financial support

WordNet sense 2 (the financial means whereby one lives):

keep, livelihood, living, sustenance

WordNet sense 3 (a subordinate musical part; provides background for more important parts):

accompaniment, backup, musical accompaniment

WordNet sense 4 (support with evidence or authority or make more certain or confirm):

corroborate, underpin, bear out

WordNet sense 5 (give moral or psychological support, aid, or courage to):

back up

WordNet sense 6 (be behind; approve of):

back, endorse, indorse, plump for, plunk for

WordNet sense 7 (be the physical support of; carry the weight of):

hold, sustain, hold up

WordNet sense 8 (the act of bearing the weight of or strengthening):

supporting

WordNet sense 9 (a military operation (often involving new supplies of men and materiel) to strengthen a military force or aid in the performance of its mission):

reinforcement, reenforcement

WordNet sense 10 (be a regular customer or client of):

patronage, patronize, patronise, keep going

WordNet sense 11 (argue or speak in defense of):

defend, fend for

WordNet sense 12 (adopt as a belief):

subscribe

WordNet sense 13 (put up with something or somebody unpleasant):

abide, bear, brook, digest, endure, stand, stomach, suffer, tolerate, digest, put up, stick out

WordNet sense 14 (establish or strengthen as with new evidence or facts):

affirm, confirm, substantiate

WordNet sense 15 (documentary validation):

documentation