Other forms: downrightly
The adjective downright is used to emphasize something, or to mean "utterly." For example, you could say that your brother's loud and junky old car is a downright embarrassment.
Downright works as an adjective or adverb, so you can describe your dad's brownies as downright delicious, your sister's terrible jokes as downright awful, or your loss of the spelling bee as a downright disgrace. In the thirteenth century, downright meant "straight down," but it had changed by 1300, to instead mean "thoroughly."