Longman Dictionary of Contemporary English homepage

Sense: 1, 3-7, 9
Origin: Old English fleoge
Sense: 2, 8, 10
Date: 1800-1900
Origin: FLY1

fly

3 noun
     
Related topics: Clothes, Baseball, Other Sports, Insects
fly3 plural flies [countable]
1

insect

HBI a small flying insect with two wings:
There were flies buzzing all around us.
2

trousers

especially American English also flies [plural] British EnglishDCC the part at the front of a pair of trousers which you can open:
He quickly did up his fly.
Your flies are undone.
3

somebody wouldn't hurt/harm a fly

informal used to say that someone is very gentle and is not likely to hurt anyone
4

be dying/dropping etc like flies

informalMI used to say that a lot of people are dying or becoming ill
5

a fly in the ointment

informal the only thing that spoils something and prevents it from being successful:
The only fly in the ointment was Jacky.
6

be a fly on the wall

to be able to watch what happens without other people knowing that you are there:
I wish I'd been a fly on the wall during that conversation.
fly-on-the-wall
7

there are no flies on somebody

British English spoken used to say that someone is not stupid and cannot be tricked
8TD

on the fly

a) technical while a computer program is actually running:
The code is translated on the fly.
b) while dealing with a situation, rather than before dealing with it:
So far, policy is being made on the fly.
9

fishing

DSO a hook that is made to look like a fly and is used for catching fish
10

baseball

DSB a fly ball

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