What does "caesura" mean?

Caesura: A metrical break in a verse, occurring in the middle of a foot and commonly near the middle of the verse; a sense pause in the middle of a foot. Also, a long syllable on which the cæsural accent rests, or which is used as a foot. Note: In the following line the cæsura is between study and of. The prop | er stud | y || of | mankind | is man.