If you say boys will be boys, for example when a group of men are behaving noisily or aggressively, you are suggesting in a light-hearted way that this is typical male behaviour and will never change.
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boys will be boys in British English
youthful indiscretion or exuberance must be expected and tolerated
See full dictionary entry for boy
boys will be boys
said to excuse the noisy or rough way a boy is behaving by saying that it is normal for boys to be noisy and rough
`Your troubles are just beginning,' they would say, shaking their heads. `Boys willbe boys.'