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

unaccountable \un`account"able\, a.
   1. not accountable or responsible; free from control.
      --south.
      1913 webster

   2. not to be accounted for; inexplicable; not consonant with
      reason or rule; strange; mysterious.
      1913 webster -- un`account"ableness, n. --
      un`account"ably, adv.
      1913 webster
      1913 webster
see also:
un`account"ableness un`account"ably 

[2] : WordNet (r) 2.0

unaccountably
     adv : in an unaccountable manner; "in the book, a tycoon
           unaccountably becomes the hero's friend"

Unaccountably >> U Words
Unaccountably, definition of term: Unaccountably
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