The Collaborative International Dictionary of English v.0.48:

Premeditation \Pre*med`i*ta"tion\, n. [L. praemeditatio: cf. F.
   pr['e]m['e]ditation.]
   The act of meditating or contriving beforehand; previous
   deliberation; forethought.
   [1913 Webster]

WordNet (r) 3.0 (2006):

premeditation
    n 1: planning or plotting in advance of acting [syn:
         premeditation, forethought]
    2: (law) thought and intention to commit a crime well in advance
       of the crime; goes to show criminal intent

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "premeditation":
   aforethought, calculatedness, calculation, caution, deliberateness,
   deliberation, express intention, expressness, forethought,
   frame-up, intentionality, packed deal, packed jury, planning,
   plotting, prearrangement, preconcertedness, preconsideration,
   predeliberation, predetermination, preordering, preresolution,
   put-up job, rigged jury, scheming, setup, stacked deck