A dog in the manger意思

"A dog in the manger" is an English idiom that means someone who selfishly prevents others from using or enjoying something, even though they themselves have no use for it. The phrase is derived from a fable by Aesop, in which a dog refuses to move from a manger (a structure for feeding livestock), preventing the cattle from eating the hay, despite the fact that the dog cannot eat the hay itself.

The idiom is used to describe a situation where someone's selfish behavior prevents others from benefiting, even when there is no logical reason for the person to be possessive or defensive over the thing in question. It is often used as a criticism of someone's behavior, implying that they are being unnecessarily obstructive or selfish.