Definition of lose verb from the Oxford Advanced Learner's Dictionary

Oxford3000

lose

verb
luːz
 
; luːz
 
lost, lost
lɒst
 
; lɔːst
 
; lɑːst
 
 
 

not find

1 [transitive] lose something/somebody to be unable to find something/somebody
Synonym
mislay
I've lost my keys.The tickets seem to have got lost.She lost her husband in the crowd.
 

have something/somebody taken away

2 [transitive] lose something/somebody to have something/somebody taken away from you as a result of an accident, getting old, dying, etcShe lost a leg in a car crash.to lose your hair/teeth(= as a result of getting old)He's lost his job.Some families lost everything(= all they owned) in the flood.They lost both their sons (= they were killed) in the war.The ship was lost at sea(= it sank).Many people lost their lives(= were killed).3 [transitive] lose something (to somebody/something) to have something taken away by somebody/somethingThe company has lost a lot of business to its competitors.4 [transitive] lose something to have to give up something; to fail to keep somethingYou will lose your deposit if you cancel the order.Sit down or you'll lose your seat.
 

have less

5 [transitive] lose something to have less and less of something, especially until you no longer have any of itHe lost his nerve at the last minute.She seemed to have lost interest in food.At that moment he lost his balance and fell.I've lost ten pounds since I started this diet.The train was losing speed.
 

not win

6 [transitive, intransitive] to be defeated; to fail to win a competition, a court case, an argument, etclose something (to somebody) to lose a game/a race/an election/a battle/a warlose to somebody We lost to a stronger team.lose (something) (by something) He lost by less than 100 votes.
 

not keep

7 [transitive, intransitive] to fail to keep something you want or need, especially money; to cause somebody to fail to keep somethinglose something The business is losing money.Poetry always loses something in translation.lose something (on something/by doing something) You have nothing to lose by telling the truth.lose on something/by doing something We lost on that deal.lose somebody something His carelessness lost him the job.
 

not understand/hear

8 [transitive] lose something to fail to get, hear or understand somethingHis words were lost (= could not be heard) in the applause.9 [transitive] lose somebody (informal) to be no longer understood by somebodyI'm afraid you've lost me there.
 

escape

10 [transitive] lose somebody/something to escape from somebody/something
Synonym
evade
, shake off
We managed to lose our pursuers in the darkness.
 

time

11 [transitive] lose something to waste time or an opportunityWe lost twenty minutes changing a tyre.Hurry— there's no time to lose!He lost no time in setting out for London.12 [transitive, intransitive] lose (something) if a watch or clock loses or loses time, it goes too slowly or becomes a particular amount of time behind the correct timeThis clock loses two minutes a day.
Opposite
gain
Idioms
Most idioms containing lose are at the entries for the nouns and adjectives in the idioms, for example lose your bearings is at bearing. 

lose it

(informal) to be unable to stop yourself from crying, laughing, etc; to become crazyThen she just lost it and started screaming.
Phrasal verbs

lose yourself in something

to become so interested in something that it takes all your attention

lose out (on something)

(informal) to not get something you wanted or feel you should haveWhile the stores make big profits, it's the customer who loses out.

lose out to somebody/something

(informal) to not get business, etc. that you expected or used to get because somebody/something else has taken itSmall businesses are losing out to the large chains.