Faltering, a.
Hesitating; trembling. "With faltering speech." Milton. -- n.
Falter; halting; hesitation. -- Fal"ter*ing*ly, adv.
Shades of meaning
Fernald has no entry of its own for faltering; he lists it under faint.
Where he writes about it:
A person may be faint when physically wearied, or when overcome with fear; he may be a faint adherent because naturally feeble or purposeless, or because half-hearted in the cause; he may be a faltering supporter because naturally irresolute or because faint-hearted and timid in view of perils that threaten, a listless worker, through want of mental energy and purpose. — from faint