(v. t.) To confirm; to render valid; to give legal force to.

OK accept accredit affirm amen approve assay attest audit authenticate authorize autograph back back up bear out bolster bring to test buttress certificate certify charter check check and doublecheck check out check over circumstantiate collate confirm constitute corroborate cosign countersign cross-check cut and try declare lawful decree document double-check empower enable enact endorse enfranchise entitle essay establish experiment formulate fortify franchise give a try give a tryout give official sanction give permission give power give the go-ahead give the imprimatur give thumbs up have a go initial justify legalize legislate legitimate legitimatize legitimize license make a regulation make legal notarize ordain pass pass on pass upon patent permit play around with practice upon prescribe privilege probate prove put in force put to trial ratify recheck regulate reinforce research road-test rubber stamp rubber-stamp run a sample sample sanction say amen to seal second shake down sign sign and seal strengthen subscribe to substantiate support sustain swear and affirm swear to taste test triple-check try try it on try out undergird undersign underwrite uphold verify visa vise warrant