not appropriate in application; defective; "an infelicitous remark"; "infelicitous phrasing"; "the infelicitous typesetting was due to illegible copy"
marked by or producing unhappiness; "infelicitous circumstances"; "unhappy caravans, straggling afoot through swamps and canebrakes"- American Guide Series
after the expected or usual time; delayed; "a belated birthday card"; "I'm late for the plane"; "the train is late"; "tardy children are sent to the principal"; "always tardy in making dental appointments"
an estimation that is too low; an estimate that is less than the true or actual value
make too low an estimate of; "he underestimated the work that went into the renovation"; "Don't underestimate the danger of such a raft trip on this river"