MissM

mut·ter (mtr)
v. mut·tered, mut·ter·ing, mut·ters
v.intr.
1. To speak indistinctly in low tones.
2. To complain or grumble morosely.
v.tr.
To utter or say in low indistinct tones.
n.
A low grumble or indistinct utterance.