The Collaborative International Dictionary of English v.0.48:

Scansion \Scan"sion\, n. [L. scansio, fr. scandere, scansum, to
   climb. See Scan.] (Pros.)
   The act of scanning; distinguishing the metrical feet of a
   verse by emphasis, pauses, or otherwise.
   [1913 Webster]

WordNet (r) 3.0 (2006):

scansion
    n 1: analysis of verse into metrical patterns