Definition of "round-mouthed" []

• In zoology, having a mouth without any lower jaw; cyclostomous: specifically noting the Cyclostomi, or lampreys and hags.

The Century Dictionary (Public Domain)

• "They had emerged from a round-mouthed tunnel -- it looked already like a rabbit-hole, so huge was the cliff behind -- on to a ledge of rock that formed a sort of road along one side of a mile-wide chasm."
• "The image of someone plummeting through this nether world, struggling round-mouthed to scream, nothing but bubbles streaming out, filled his head."
• "The girl against the wall looked at Gaia with a big-eyed, round-mouthed expression that could have been fear or hope or stupidity."