To be defeated by (someone). The victor can be mentioned after "to," or the lost thing can be stated between "lose" and "to." The football team lost to their rivals in the championship game. I can't believe I lost the student council presidency to that doofus!
lose something to someone
to yield or give up something in defeat to someone. We lost the case to the opposing lawyers. Mary lost her title to last year's runner-up.
lose to someone or something
to be defeated by someone or something. I lost to Wendy in the sales contest. Our team lost to the Adamsville Raiders for the seventh year in a row.