portamento [It.]

A continuous movement from one pitch to another through all of the intervening pitches, without, however, sounding these discretely. It is principally an effect in singing and string playing, though for the latter and for other instruments capable of such an effect, the term glissando is often used. In vocal music, the portamento may be indicated by connecting with a slur two pitches that are sung to different syllables. If two pitches are sung to the same syllable, with the slur simply indicating this fact, a portamento is indicated by the term itself.