(prosody) a line of poetry having an extra syllable or syllables at the end of the last metrical foot.

What is an extra syllable called?

hy·per·cat·a·lec·tic

Having an extra syllable or syllables at the end of a metrically complete line of verse or in a metrical foot. ... hy′per·cat′a·lex′is (-kăt′l-ĕk′sĭs) n.

What is catalectic in prosody?

catalectic - (prosody) a line of verse that lacks a syllable in the last metrical foot.