The Collaborative International Dictionary of English v.0.48:

man hour \man hour\, man-hour \man-hour\n.
   The quantity of work which one person can perform in one
   hour; -- often an estimate made for the purpose of deciding
   whether to undertake a project, and sometimes used in
   accounting; as, it will take a hundred man-hours to write the
   program.
   [PJC]

WordNet (r) 3.0 (2006):

man hour
    n 1: a time unit used in industry for measuring work [syn: man
         hour, person hour]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "man hour":
   abundant year, academic year, annum, bissextile year,
   calendar month, calendar year, century, common year, day, decade,
   decennary, decennium, defective year, fiscal year, fortnight, hour,
   leap year, lunar month, lunar year, lunation, luster, lustrum,
   microsecond, millennium, millisecond, minute, moment, month, moon,
   quarter, quinquennium, regular year, second, semester, session,
   sidereal year, solar year, sun, term, trimester, twelvemonth, week,
   weekday, year