WordNet (r) 3.0 (2006):

Joel
    n 1: a Hebrew minor prophet
    2: an Old Testament book telling Joel's prophecies [syn: Joel,
       Book of Joel]

Easton's 1897 Bible Dictionary:

Joel
   Jehovah is his God. (1.) The oldest of Samuel's two sons
   appointed by him as judges in Beersheba (1 Sam. 8:2). (See
   VASHNI ¯(n/a).) (2.) A descendant of Reuben (1 Chr. 5:4,8). (3.)
   One of David's famous warriors (1 Chr. 11:38). (4.) A Levite of
   the family of Gershom (1 Chr. 15:7, 11). (5.) 1 Chr. 7:3. (6.) 1
   Chr. 27:20. (7.) The second of the twelve minor prophets. He was
   the son of Pethuel. His personal history is only known from his
   book.


Hitchcock's Bible Names Dictionary (late 1800's):

Joel, he that wills or commands