plural of profitability

(video games) Initialism of massively multiplayer online game. / (aviation) Maximum operating Mach number; the Mach number which an aircraft should not exceed in the course of routine operation.

plural of Voronoi cell

(chiefly poetic, Greek mythology) Of or relating to the river Lethe, one of the four rivers of Hades. Those who drank from it experienced complete forgetfulness.