WordNet (r) 3.0 (2006):

Haggai
    n 1: a Hebrew minor prophet [syn: Haggai, Aggeus]
    2: an Old Testament book telling the prophecies of Haggai which
       are concerned mainly with rebuilding the temples after the
       Babylonian Captivity [syn: Haggai, Aggeus, Book of
       Haggai]

Easton's 1897 Bible Dictionary:

Haggai
   festive, one of the twelve so-called minor prophets. He was the
   first of the three (Zechariah, his contemporary, and Malachi,
   who was about one hundred years later, being the other two)
   whose ministry belonged to the period of Jewish history which
   began after the return from captivity in Babylon. Scarcely
   anything is known of his personal history. He may have been one
   of the captives taken to Babylon by Nebuchadnezzar. He began his
   ministry about sixteen years after the Return. The work of
   rebuilding the temple had been put a stop to through the
   intrigues of the Samaritans. After having been suspended for
   fifteen years, the work was resumed through the efforts of
   Haggai and Zechariah (Ezra 6:14), who by their exhortations
   roused the people from their lethargy, and induced them to take
   advantage of the favourable opportunity that had arisen in a
   change in the policy of the Persian government. (See DARIUS
   ¯T0000975 [2].) Haggai's prophecies have thus been
   characterized:, "There is a ponderous and simple dignity in the
   emphatic reiteration addressed alike to every class of the
   community, prince, priest, and people, 'Be strong, be strong, be
   strong' (2:4). 'Cleave, stick fast, to the work you have to do;'
   or again, 'Consider your ways, consider, consider, consider'
   (1:5, 7;2:15, 18). It is the Hebrew phrase for the endeavour,
   characteristic of the gifted seers of all times, to compel their
   hearers to turn the inside of their hearts outwards to their own
   view, to take the mask from off their consciences, to 'see life
   steadily, and to see it wholly.'", Stanley's Jewish Church. (See SIGNET.)


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

Haggai, feast; solemnity