Spondee in the ancient metric is a foot with two long (stressed) syllables. The poems written with the help of this foot were intended in ancient Greece to celebrate the gods. Spondee was mainly used in an ancient hexameter which consists mainly of dactylic feet.
It’s easy to define spondee. Firstly, you should define the main foot, and then you will find where this foot “breaks” in some way. When you see 2 stressed syllables standing together and if they do not fit the main foot, be sure that this is a spondee.
“If I do prove her haggard,
Though that her jesses were my dear heart-strings …”
Othello by William Shakespeare
O dark, dark, dark, amid the blaze of noon,
Irrecoverably dark, total eclipse
Without all hope of day!
Samson Agonistes by John Milton