toss vs toss back

toss is a noun but toss back is not a noun.

Word	Noun	Adjective	Verb	Adverb
toss	Yes	No	Yes	No
toss back	No	No	Yes	No

As verbs, toss back is a hyponym of toss; that is, toss back is a word with a more specific, narrower meaning than toss:

Other hyponyms of toss include submarine, lag, throw back.

toss (noun)	toss back (noun)
(sports) the act of throwing the ball to another member of your team
the act of flipping a coin
an abrupt movement

toss (verb)	toss back (verb)
agitate	throw back with a quick, light motion
throw or toss with a light motion
throw carelessly
lightly throw to see which side comes up
move or stir about violently
throw or cast away