unbeknown

from WordNet (r) 3.0 (2006)

unbeknown
    adv 1: without someone's knowledge; "unbeknownst to me, she made
           all the arrangements" [syn: {unbeknown}, {unbeknownst}]
    adj 1: (usually used with `to') occurring or existing without
           the knowledge of; "a crisis unbeknown to me"; "she had
           been ill for months, unbeknownst to the family" [syn:
           {unbeknown(p)}, {unbeknownst(p)}]

from The Collaborative International Dictionary of English v.0.48

Unbeknown \Un`be*known"\, a.
   Not known; unknown. [Colloq.]
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

34 Moby Thesaurus words for "unbeknown":
      able, enigmatic, incalculable, incognizable, mysterious, puzzling,
      sealed, strange, unapparent, unapprehended, unascertained,
      uncharted, unclassified, undisclosed, undiscoverable, undiscovered,
      undivulged, unexplained, unexplored, unexposed, unfamiliar,
      unfathomed, unheard, unheard-of, unidentified, uninvestigated,
      unknowable, unknown, unperceived, unplumbed, unrevealed,
      unsuspected, untouched, virgin

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