subject field

NOUN
13 LETTERS · STARTS WITH S

subject field is a valid 13-letter word worth 27 points in Scrabble and 33 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
S1U1B3J8E1C3T1F4I1E1L1D2
1 + 1 + 3 + 8 + 1 + 3 + 1 + 0 + 4 + 1 + 1 + 1 + 2 =27 PTS
DOUBLE WORD → 54TRIPLE WORD → 81
MEANING

What does subject field mean?