stack away

VERB
10 LETTERS · STARTS WITH S

stack away is a valid 10-letter word worth 21 points in Scrabble and 21 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
S1T1A1C3K5A1W4A1Y4
1 + 1 + 1 + 3 + 5 + 0 + 1 + 4 + 1 + 4 =21 PTS
DOUBLE WORD → 42TRIPLE WORD → 63
MEANING

What does stack away mean?