Tenuto (Italian, past participle of tenere "to hold") is a direction used in musical notation. Arguably, it is one of the first directions to be used in music notation, as Notker of St. Gall (c.840 - 912) discusses the use of the letter t in plainsong notation as meaning trahere vel tenere debere in one of his letters.
Tenuto can mean either hold the note in question its full length (or longer, with slight rubato) or else play the note slightly louder. In other words, the tenuto mark is sometimes interpreted as an articulation mark and sometimes interpreted as a dynamic mark. When it appears in conjunction with an accent mark, it is of course taken as an indication of articulation, and, conversely, when it appears in conjunction with a staccato mark, it is taken as an indication of a slight dynamic accent. When it appears by itself, its meaning must be determined by its musical context.
In rudimental (drumline) drumming, the tenuto marking is traditionally interpreted by giving the marked note a slight accent or emphasis.