Definition: Acidly means extremely bitter or sour. It's a word derived from Greek, meaning "to be sour" or "to be very sour." This adjective can mean "very sour" (a verb form), to describe something that is sour; or it could also mean that someone or something is very sour in taste. The word 'acidially' comes from the same origin as 'acidly' and means "in a very sour manner." It's another adverb meaning "with extreme bitterness." So, to summarize, acidically means extremely bitter or sour, while acidially has two possible meanings: with extreme bitterness (in a very sour manner) and in a very sour manner.