[1] : The Collaborative International Dictionary of English v.0.48

when \when\, adv. oe. when, whan, whenne, whanne, as.
   hwaenne, hwanne, hwonne; akin to os. hwan, od. wan, ohg.
   wanne, g. wann when, wenn if, when, goth. hwan when, and to
   e. who. ????. see who.
   1913 webster
   1. at what time; -- used interrogatively.
      1913 webster

            when shall these things be?           --matt. xxiv.
                                                  3.
      1913 webster

   note: see the note under what, pron., 1.
         1913 webster

   2. at what time; at, during, or after the time that; at or
      just after, the moment that; -- used relatively.
      1913 webster

            kings may
            take their advantage when and how they list.
                                                  --daniel.
      1913 webster

            book lore ne'er served, when trial came,
            nor gifts, when faith was dead.       --j. h.
                                                  newman.
      1913 webster

   3. while; whereas; although; -- used in the manner of a
      conjunction to introduce a dependent adverbial sentence or
      clause, having a causal, conditional, or adversative
      relation to the principal proposition; as, he chose to
      turn highwayman when he might have continued an honest
      man; he removed the tree when it was the best in the
      grounds.
      1913 webster

   4. which time; then; -- used elliptically as a noun.
      1913 webster

            i was adopted heir by his consent;
            since when, his oath is broke.        --shak.
      1913 webster

   note: when was formerly used as an exclamation of surprise or
         impatience, like what
         1913 webster

               come hither; mend my ruff:
               here, when thou art such a tedious lady --j.
                                                  webster.
         1913 webster

   when as, when that, at the time that; when. obs.
      1913 webster

            when as sacred light began to dawn.   --milton.
      1913 webster

            when that mine eye is famished for a look. --shak.
      1913 webster
see also:
who what when as when that 

[2] : WordNet (r) 2.0

when
     adv : as soon as; "once we are home, we can rest" syn: once
see also:
once 

[3] : Moby Thesaurus II by Grady Ward, 1.0

43 moby thesaurus words for "when":
   after all, again, albeit, all the same, although, anon, as far as,
   as long as, at all events, at any rate, at what time, at which,
   at which time, but, during which time, even, even so, for all that,
   howbeit, however, in any case, in any event, in what period,
   in which time, just the same, nevertheless, nonetheless,
   notwithstanding, on what occasion, on which occasion, rather,
   still, the while, though, upon which, what time, when as, whenever,
   whereas, whereupon, while, whilst, yet

[4] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

when. at which time, in wills, standing by itself unqualified and 
unexplained, this is a word of condition denoting the time at which the gift 
is to continence. 6 ves. 243; 2 meriv. 286. 
     2. the context of a will may show that the word when is to be applied 
to the possession only, not to the vesting of a legacy; but to justify this 
construction, there must be circumstances, or other expressions in the will, 
showing such to have been the testator's intent. 7 ves. 422; 9 ves. 230 
coop. 145; 11 ves. 489; 3; bro. c. c. 471. for the effect of the word when 
in contracts and in wills in the french law, see 6 toull. n. 520. 

When >> W Words
When, definition of term: When
when_pag1.html

Only When >> O Words
Only When, definition of term: Only When
only+when_pag1.html