Meaning of “alternate” - Learner’s Dictionary

alternate

verb uk us /ˈɔːltəneɪt/

[ I ] If two things alternate, one thing happens, then the other thing happens, then the first thing happens again, etc.:

She alternates between cheerfulness and deep despair.
alternate sth with sth

to use or do one thing then another thing and then the first thing again, etc:

They alternate classical pieces with more modern works.
alternating adjective

alternating moods of anger and sadness

(Definition of “alternate verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)