Meaning of “besides” - Learner’s Dictionary

besides

adverb uk us /bɪˈsaɪdz/
ANOTHER REASON

B1 used to give another reason for something:

She won't mind if you're late - besides, it's not your fault.
ALSO

B1 in addition to:

Besides looking after the children, she also runs a successful business.

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