fal·ter 
(fôltər)
(fôltər)intr.v. fal·tered, fal·ter·ing, fal·ters
1. To be unsteady in purpose or action, as from loss of courage or confidence; waver: "She never faltered in her resolution to regain her old position" (Louis Auchincloss).
2. To speak hesitatingly; stammer: faltered in reciting the poem.
3.
a. To move unsteadily or haltingly; stumble: The racehorse faltered right after the start.
b. To become weak, ineffective, or unsteady, especially in performance: The economy faltered in the second quarter. His memory began to falter.
n.
1. Unsteadiness in speech or action: finished the project without falter.
2. A faltering sound: answered with a falter in his voice.
[Middle English falteren, to stagger, possibly from Old Norse faltrask, to be puzzled, hesitate.]
falter·er n.
falter·ing·ly adv.