underhead /ˈʌndə(ɹ)hɛd/noun 4adjective 3adverb 1forms 3 noun4 •The area directly below the head of something. (any sense)The valves were removed from the engine at 25 hour intervals and zyglo inspected for cracks in the underhead and stem. — 1981 •The base of a railroad track. •(old-fashioned) direct costs.I think prices would go up, for I know something of the importance of overhead and underhead cost as affecting the price of the goods you have to sell. — 1911 •(no longer used) A blockhead, or stupid person; a dunderhead.wiser discretions, that have the thread of reason to conduct them, offend without a pardon; whereas underheads may stumble without dishonour. — 1642 adjective3 •Beneath the head of a mechanical component.With large underhead radius shown to be optimum in a given case, the judgment must be made as to whether the valve weight increase is justified in improved engine performance. — 1995 •Coming from below.It should almost be a lighting axiom therefore, that brilliant underhead light sources are taboo for esthetic purposes. — 1931 •Such that the train track goes over the pathway of cars or pedestrians.We further find that the viaduct or overhead plan will be more economical than the subway or underhead plan. — 1921 adverb1 •In an underhead location.The pillow was warm underhead, the kind of warmth that is slightly perverse and misplaced, the warmth of a bed after lunch, as you rub your cheek against the linen and wonder what you can do. — 1940 formsunderheads · more underhead · most underhead