not say boo to a fly

not say boo to a fly

To be particularly shy, diffident, or timid by nature. Primarily heard in Australia. My brother is a very sweet, warm-hearted man who wouldn't say boo to a fly. How can you suspect him of committing this crime? The neighbour's daughter is just the cutest little thing, but she couldn't say boo to a fly.

See also: boo, fly, not, say, to

Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.