An unsteady movement of the body in walking or standing as if one were about to fall; a reeling motion

“the stagger of a drunken man”

A disease of horses and other animals, attended by reeling, unsteady gait or sudden falling

“apoplectic or sleepy staggers”

Bewilderment; perplexity.

Sway unsteadily, reel, or totter.

Doubt, waver, be shocked.

Have multiple groups doing the same thing in a uniform fashion, but starting at different, evenly-spaced, times or places (attested from 1856).