1. To vote in an election or other such contest in which votes are collected; to vote. You seem happy about the results of the election. I guess I know which candidate you cast your vote for! I need to go to the polling place and cast my vote!

2. To share one's opinion on something (which could involve informal "voting"). If I get a say in the matter, I cast my vote in favor of a new microwave for the break room! Raise your hand to cast your vote for lower monthly dues!