Webster’s Revised Unabridged Dictionary · 1913 Oblongum Ob·lon′gum, n.; pl. Oblonga (#). [NL. See Oblong.] (Geom.) A prolate spheroid; a figure described by the revolution of an ellipse about its greater axis. Cf. Oblatum, and see Ellipsoid of revolution, under Ellipsoid. ‹ Oblongness Obloquious ›