What does "underdressed" mean? When can I use this expression?

Rebecca

"Underdressed" refers to being dressed too informally for an occasion. For example, in many cases, attending a wedding wearing jeans, a t-shirt and sneakers would be considered "underdressed". You can use "underdressed" to describe someone who is not dressed nice enough for a role or event. Ex: I feel underdressed, everyone at this party is wearing a dress, and I am wearing sweatpants. Ex: He is underdressed for his new job, he is wearing a t-shirt when he should be wearing a dress shirt.