A "shirt dress" refers to a piece of clothing that combines the features of a shirt and a dress. It usually has a similar style to a collared button-up shirt but is longer in length, resembling a dress. Full definition
You can't go wrong with shirt dress for spring, it's my favorite go - to! (peachesinapod.com)
I kept it comfy with this soft grey t shirt dress from Gap, but added a pair of wedges and a fun hairstyle to make it a little more special. (themotheroverload.com)