Real Dictionary

lose
verb: If someone loses a quality, characteristic, attitude, or belief, they no longer have it.
verb: If you lose a contest, a fight, or an argument, you do not succeed because someone does better than you and defeats you.
verb: If you lose something, you do not know where it is, for example because you have forgotten where you put it.
verb: You say that you lose something when you no longer have it because it has been taken away from you or destroyed.

lose in American English
to bring to ruin or destruction
intransitive verb: to suffer loss
transitive verb: to come to be without (something in one's possession or care), through accident, theft, etc., so that there is little or no prospect of recovery

lose in British English
verb: to part with or come to be without, as through theft, accident, negligence, etc