From The Collaborative International Dictionary of English v.0.48 :
Quarter round \Quar"ter round`\ (Arch.)
An ovolo.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
quarter round
n 1: a convex molding having a cross section in the form of a
quarter of a circle or of an ellipse [syn: ovolo,
thumb, quarter round]