Definition of “past” - Learner’s Dictionary

past

noun us uk /pɑːst/
the past

B1 the time before the present and all the things that happened then:

the distant/recent past
In the past people would bathe once a month.

A2 the form of the verb which is used to show what happened in the past

More examples

sb's past

B1 all of the things that someone has done in their life:

I knew nothing about his past.

(Definition of “past noun” from the Cambridge Learner's Dictionary © Cambridge University Press)