Meaning of “understanding” - Learner’s Dictionary

understanding

adjective us uk /ˌʌndəˈstændɪŋ/
Thanks for being so understanding.Her employer is very understanding.Try and be more understanding.He's not usually so understanding.My boss wasn't very understanding.

B2 showing sympathy for someone's problems:

Fortunately, my girlfriend is very understanding.

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