A trochaic foot (trochee) has a long syllable followed by a short syllable (LS or /U).
Hexameter is six feet to the line.
This example is actually the first two verses of a hymn. While the lines are hexameter, not all of the feet are trochaic (as we’ve seen, poets tend to mix up their feet for rhythmic effect), but the repetition of “holy, holy, holy” is most definitely trochaic, as well as phrases such as “Merciful and mighty”, “Early in the morning” and “Casting down their golden crowns”.
Holy, holy, holy! Lord God Almighty!
Early in the morning our song shall rise to Thee;
Holy, holy, holy, merciful and mighty!
God in three Persons, blessed Trinity!
Holy, holy, holy! All the saints adore Thee,
Casting down their golden crowns around the glassy sea;
Cherubim and seraphim falling down before Thee,
Who was, and is, and evermore shall be.
Reginald Heber – Holy, Holy, Holy
A closer look at the feet in this verse
U = short syllable; / = long syllable; | = division between feet