A hovering accent is a stress that can fall on either of two adjacent syllables in a word or phrase, so the poet or reader can shift the emphasis to suit the meter. It is often discussed in relation to sprung rhythm and other meters that allow more flexibility than a strict pattern of stressed and unstressed syllables.
Example
Bright-GLASS or BRIGHT-glass, the meter lets the beat decide
which syllable leans forward, which one glides beside it.