SUPINE, in Latin grammar, part of the conjugation of a verb, being a verbal substantive of the singular number and the fourth declension.
There are two kinds of supines: one, called the first supine, ending in um of the accusative case, which is always of an active signification, and follows a verb of motion; as abii deambulatum. The other called the last supine, and ending in u of the ablative case, is of a passive signification, and is governed by substantives or adjectives; as, facile dictu, &c.
They have their name, says Probus, and after him Vossius,
Vossius, quod ad instar supinorum et otiosorum hominum omnia habent confusa: or, according to Priscian, quod nascantur a participiis passivis, quæ supina appellata sunt, quia in infimo loco sita, totam conjugationis molem suscipiant.