The Collaborative International Dictionary of English v.0.48:

burn out \burn out\ v. i.
   1. To burn till the fuel is exhausted; as, when the candle
      burned out the room was totally dark; the firefighters
      couldn't control the oil tank fire and had to let it burn
      out by itself.
      [1913 Webster +PJC]

   2. To stop functioning due to failure of some component
      caused by the heat of the electrical current used in its
      operation; -- of electrical devices.
      [PJC]

   3. To become apathetic or depressed, and cease to function
      effectively, due to the fatigue and frustration of
      prolonged stress and overwork; -- of people; as, the
      stress in the bond market is so great that many traders
      burn out after only ten years on the job.
      [PJC]

WordNet (r) 3.0 (2006):

burn out
    v 1: melt, break, or become otherwise unusable; "The lightbulbs
         blew out"; "The fuse blew" [syn: blow out, burn out,
         blow]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "burn out":
   beat, blow, break down, collapse, crack up, debilitate, die,
   die away, die out, do in, do up, droop, drop, enervate, exhaust,
   fag, fag out, faint, fatigue, fizzle, fizzle out, flag, flame out,
   frazzle, gasp, get tired, give out, go out, grow weary, harass,
   jade, knock out, knock up, overfatigue, overstrain, overtire,
   overweary, pant, peter out, play out, poop, poop out, prostrate,
   puff, puff and blow, run down, run out, sink, succumb, tire,
   tire out, tire to death, tucker, use up, weaken, wear, wear down,
   wear on, wear out, weary, wheeze, wilt, wind