Is this word on the boggle board?
Javascript (E6) 137 160 175 190

Less than 2*Golfscript. Moral victory ...

F=a=&gt;[...a].some((e,p,b)=&gt;(Q=(p,n)=&gt;p&gt;29||b[p]!=b[n]||(b.r|=!b[++n])||(b[p]=b[n+~[1,5,6,7].map(q=&gt;Q(p+q,n)|Q(p-q,n),b[p]=0)]))(p,30)&amp;b.r)


Edit Golfed code reorganization. Again and again

Ungolfed Last version, a bit tricky to follow

F = a =&gt; 
  [...a] // input string to array, 30 chars of board then the target word
  .some ( // use some to scan the board, return true when found
      (e,p,b)=&gt; // params to callback: element, position, complete array 
      (         // NB array b has no .r property, so use it for return value (it's undefined at start) 
        Q = (p,n) =&gt;         // Scan function, p=position in board, n=nth char of target word
          p &gt; 29 ||          // Chaek if going outside the board to the target word
          b[p] != b[n] ||    // if invalid char at current position, return
          (b.r |= !b[++n]) ||  // if at end of target, set r to 1 and return (also increment n )
          (                  // else... (NB next tree lines are coalesced in golfed code)
            b[p] = 0,        // remove current char (to avoid reusing) 
            [1,5,6,7].map( q =&gt; Q(p+q,n)|Q(p-q,n)), // recursive call for + - 1,5,6,7
            b[p] = b[n-1]    // put current char into array again 
          )
      )(p,30) &amp; b.r // initial position 0 in target word is 30 in the array
  ) 


Ungolfed First version , should be clearer

F = a =&gt; (
  b = a.split('\n'),
  w = b.pop(),
  r = 0,
  Q = (p, n) =&gt; 
    (r |= !w[n]) || 
    (
      b[p] = 0,
      [1,5,6,7,-1,-5,-6,-7].map( q =&gt; b[q+=p]==w[n] &amp;&amp; Q(q,n+1)),
      b[p] = w[n-1]
    ),
  b = [...b+''],
  b.map((e, p) =&gt; e==w[0] &amp;&amp; Q(p,1)),
  r
)


Usage 

F("AJNES\nTNFTR\nLSAIL\nUDNEX\nEQGMM\nLIFTS\nDAFTER")


Test

['DAFTER', 'STANDS', 'LIFTS', 'FATE', 'DATING' ,
 'SADDEN','SULTANS', 'EXIST', 'SUEDE', 'QUEST']
.map(w =&gt; [w, F("AJNES\nTNFTR\nLSAIL\nUDNEX\nEQGMM\n" +w)])


Output:

[["DAFTER", true], ["STANDS", true], ["LIFTS", true], ["FATE", true], ["DATING", true], 
["SADDEN", false], ["SULTANS", false], ["EXIST", false], ["SUEDE", false], ["QUEST", false]]