lose track of someone or something Definition

lose
verb lost, losing

1a. To fail to keep or obtain something, especially because of a mistake, carelessness, etc;

Example: lost his money through a hole in his pocket
1b. To stop or begin to stop having (some distinguishing quality, characteristic or property);

Example: She was losing her nerve
Example: Despite everything, he hasn't lost his sense of humour
1c. To become less marked, noticeable, intense, etc in a specified way.

Example: These roses have lost their smell
2a. To misplace something, especially temporarily;

Example: I've lost the car keys
Thesaurus: misplace, mislay, forget; Antonym: find.
2b. To be unable to find something;
2c. To leave accidentally.

Example: I lost the umbrella at the cinema
3a. To suffer the loss of someone (usually a close friend or relative) through death;
3b. To suffer the loss of (an unborn baby) through miscarriage or stillbirth;
3c. To fail to save the life of (especially a patient);
3d. To be deprived of someone or something (life, possessions, etc), especially in a war, fire, natural disaster, etc;

Example: The village lost half its population in the earthquake
3e. To be killed or drowned, especially at sea.

Form: be lost
4. To fail to use or get something; to miss (an opportunity).

Thesaurus: miss, forfeit.
tr & intr
5a. To fail to win (a game, vote, proposal, election, battle, bet, etc);

Thesaurus: be defeated, fail, succumb; Antonym: win.
5b. To give away; to forfeit.

Example: lost £50 on the horses
6a. To be unable or no longer able to hear, see, understand, etc someone or something;

Example: Sorry, I lost what you said when that noisy bus went by
6b. To confuse or bewilder someone.

Example: Sorry, you've lost me there
7a. To escape or get away from someone or something;
7b. Said of a competitor in a race, etc: to leave (the rest of the field, etc) behind.
8. Said of a clock or watch: to become slow by (a specified amount).

Idiom: lose one's cool

colloq
To become upset.

Idiom: lose face

To be humiliated or discredited.

Idiom: lose one's grip (lose one's grip on something)

To be unable to control or understand things.

Idiom: lose ground

To slip back or behind.
Example: Major steadily lost ground in the opinion polls

Idiom: lose one's head

To become angry or irrational.

Idiom: lose heart

To become discouraged; to despair.

Idiom: lose one's heart (lose one's heart to someone)

To fall in love (with them).

Idiom: lose one's licence

To be disqualified from driving, usually for exceeding the limit of alcohol in the blood or for driving dangerously.

Idiom: lose one's marbles

slang
To go completely crazy.

Idiom: lose one's mind (lose one's reason)

To behave irrationally, especially temporarily.

Idiom: lose one's rag (lose the rag)

(rit)
colloq
To become very angry.

Idiom: lose sight of someone or something

To be unable or no longer able to see them or it.

To forget or ignore the importance of them or it.
Example: They lost sight of their original aims

Idiom: lose sleep over something

To worry about it or be preoccupied by it.

Idiom: lose one's temper

To become angry.

Idiom: lose one's touch

To forget how to do something; to be less proficient at doing something than one used to be.

Idiom: lose touch with someone or something

To no longer be in contact with them or it.

Idiom: lose track of someone or something

To fail to notice or monitor the passing or progress of them or it.

Idiom: lose one's voice

To be unable or hardly able to speak, especially due to having a sore throat, a cold or flu.

Idiom: lose one's way (lose the way)

To be unable or no longer able to tell where one is or in which direction one should be going; to stray from one's intended route by mistake.

Etymology: Anglo-Saxon losian to be lost.

Phrasal Verb: lose oneself in something

To have all of one's attention taken up by it.

Phrasal Verb: lose out

To suffer loss or be at a disadvantage.To fail to get something one wants.

Phrasal Verb: lose out on something

To fail to benefit from it.

Phrasal Verb: lose to someone

To be beaten by them.
Example: He lost to a more experienced player

Info:

A word often confused with this one is loose.