The Collaborative International Dictionary of English v.0.48:

When \When\, adv. [OE. when, whan, whenne, whanne, AS.
   hw[ae]nne, 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.]
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   1. At what time; -- used interrogatively.
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            When shall these things be?           --Matt. xxiv.
                                                  3.
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   Note: See the Note under What, pron., 1.
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   2. At what time; at, during, or after the time that; at or
      just after, the moment that; -- used relatively.
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            Kings may
            Take their advantage when and how they list.
                                                  --Daniel.
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            Book lore ne'er served, when trial came,
            Nor gifts, when faith was dead.       --J. H.
                                                  Newman.
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   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.
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   4. Which time; then; -- used elliptically as a noun.
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            I was adopted heir by his consent;
            Since when, his oath is broke.        --Shak.
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   Note: When was formerly used as an exclamation of surprise or
         impatience, like what!
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               Come hither; mend my ruff:
               Here, when! thou art such a tedious lady! --J.
                                                  Webster.
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   When as, When that, at the time that; when. [Obs.]
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            When as sacred light began to dawn.   --Milton.
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            When that mine eye is famished for a look. --Shak.
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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



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.