From Longman Dictionary of Contemporary Englishfall in with somebody/something phrasal verb1 ACCEPTto accept someone’s ideas, decisions etc and not disagree with them Once she explained her problem, he was happy to fall in with her plans.2 to become friendly with a person or group of people after meeting them by chance SYN get in with She fell in with the wrong crowd in her teens. → fall→ See Verb table
Examples from the Corpus
fall in with • He falls in with Compeyson and helps him to discover Magwitch's hiding-place.• Sometimes agreement is apparent rather than real because of the tendency to conform and fall in with majority opinion.• I turned left and desultorily fell in with Ronny Taskin and his friends, who walked home the same way I did.• This commitment will encourage others to fall in with the change.• That was the reason why she fell in with the man she later married.• We fell in with them, as the wheels turned, and we made our way to the river bank.• I fell in with those who drew the line at violence. 