We found 3 dictionaries that define the word shut up like a clam:

General (2 matching dictionaries)

1. shut up like a clam: Cambridge Advanced Learner's Dictionary
2. shut up like a clam: Wiktionary

Miscellaneous (1 matching dictionary)

3. shut up like a clam: Idioms

Definitions from Wiktionary (shut up like a clam) ▸ verb:  Synonym of clam up ▸ Words similar to shut up like a clam ▸ Usage examples for shut up like a clam ▸ Idioms related to shut up like a clam ▸ Wikipedia articles (New!) ▸ Words that often appear near shut up like a clam ▸ Rhymes of shut up like a clam ▸ Invented words related to shut up like a clam