catalexis
noun
cat·a·lex·is ˌka-tə-ˈlek-səs 
plural catalexes ˌka-tə-ˈlek-ˌsēz
: omission or incompleteness usually in the last foot of a line in metrical verse
Word History
Etymology
New Latin, from Greek katalēxis close, cadence, from katalēgein
First Known Use
1830, in the meaning defined above