A line is a unit of poetry that takes up—you guessed it—a line of text. It's not a unit of sense or meaning (although it can be if the lines are end-stopped). It's a unit of form.
And now, Shmoop will regale you with recitations of our top ten favorite lines of poetry. Ever.
She walks in beauty like the night
L'amor che move il sole e l'altre stelle
There is no Frigate like a Book
Jazz June. We
I am large . . . . I contain multitudes.
The blackbird must be flying.
Te amo sin saber cómo, ni cuándo, ni de dónde,
Lose something every day. Accept the fluster
What form my dreaming was about to take.
Time's wingèd chariot hurrying near;
Okay, okay, eleven: