say something under one's breath

"Nice place you got here," he said under his breath.

"I was working on something else," she said under her breath.

We were too far away to hear him say, under his breath, "I hope."

But he said this under his breath and no one heard it.

Travis said something under his breath and went back inside.

"And Indian women say the most terrible things about you under their breath."

"At last you have come," she said under her breath, so the others could not hear.

"That boy has no business working," she said under her breath.

"I know my baby's running out of hands," she said under her breath.

"I should put my children to bed," he said under his breath.