We found one dictionary that defines the word let sb in on a secret:

General (1 matching dictionary)

1. let sb in on a secret: Cambridge Advanced Learner's Dictionary

▸ Words similar to let sb in on a secret ▸ Usage examples for let sb in on a secret ▸ Idioms related to let sb in on a secret ▸ Wikipedia articles (New!) ▸ Words that often appear near let sb in on a secret ▸ Rhymes of let sb in on a secret ▸ Invented words related to let sb in on a secret