Here's how it breaks down:
* Dis-: This is a prefix meaning "not" or "opposite of".
* Taste: This refers to the sense of taste or the act of tasting.
* -ful: This is a suffix meaning "full of" or "characterized by".
Therefore, "distasteful" literally means "not full of taste" or "not characterized by taste". It implies something that is unpleasant or offensive to the senses, especially the sense of taste.