Monostich

A monostich is a poem which consists of a single line.
The following is an example:

'Skunks,' the squirrel said, 'are sent to try us.'

Ralph Hodgson

A monostich could be also titled; due to the brevity of the form, the title is invariably as important a part of the poem as the verse itself:

COWARD

Bravery runs in my family.

A. R. Ammons

Some examples of one-line poems were created by Ancient authors (Martial e.g.). Modern monostich was started in Russia in 1894 when Valery Bryusov published the single line of pretty absurdic essence:

О закрой свои бледные ноги.

(Oh, cover your pale legs.)

In Western poetry monostich was reinvented by Guillaume Apollinaire in his "Chantre" (1914).