Wordnet 3.0
NOUN (1)
1.
a point equidistant from the ends of a line or the extremities of a figure;
[syn: center, centre, midpoint]
WordNet (r) 3.0 (2006):
midpoint
n 1: a point equidistant from the ends of a line or the
extremities of a figure [syn: center, centre,
midpoint]