Sell somebody short - Idioms by The Free Dictionary
sell somebody short
sell (someone, something, or oneself) short
To undervalue someone, something, or oneself; to underestimate or underappreciate the good qualities of someone, something, or oneself. Don't sell yourself short—your writing is really excellent! I know you don't like their pitcher, but don't sell him short; he's inarguably one of the best in the league. I think they're selling this short. It's actually an incredibly good deal!
sell somebody ˈshort cheat somebody by giving them less than they have paid for: He sold us short! We paid for five kilos of mushrooms and only got four!
sell yourself/somebody/something ˈshort describe yourself/somebody/something as being less good, valuable, etc. than you, etc. really are: Don’t sell yourself short when you go for an interview. ♢ It was a great idea, but you sold it short.