a line of verse with five metrical feet, each consisting of one short (or unstressed) syllable followed by one long (or stressed) syllable, for example Two households, both alike in dignity.
examples ;
It is the east, and Juliet is the sun. (William Shakespeare, Romeo and Juliet)
Her vestal livery is but sick and green
And none but fools do wear it; cast it off. (Shakespeare, Romeo and Juliet)