Similar to the sexual term, it generally means to have somebody in a favorable position, like after beating the shit out of them, and ramming any object of your choice into one of their main orifices, like their mouth or anus.
However, many people don't know how to taste with their anus, so you might as well just say it in a foreign language, like:
smak tęczy, BITCH
die smaak van die reënboog, BITCH
Mr. Maynard hid in the bathroom stall, waiting for Mr. Concubine, where he proceeded to rip his genitalia off and beat him with it. He then whipped out his OWN dinosaur penis with flaming coconuts and forcefully rammed it into Concubine's orifice while saying "TASTE THE RAINBOW, BITCH!!!!"