waste one's time

VERB
16 LETTERS · STARTS WITH W

waste one's time is a valid 16-letter word worth 18 points in Scrabble and 20 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
W4A1S1T1E1O1N1E1'0S1T1I1M3E1
4 + 1 + 1 + 1 + 1 + 0 + 1 + 1 + 1 + 0 + 1 + 0 + 1 + 1 + 3 + 1 =18 PTS
DOUBLE WORD → 36TRIPLE WORD → 54
MEANING

What does waste one's time mean?