The Collaborative International Dictionary
Bell-mouthed
Bell-mouthed \Bell"-mouthed`\, a.
Expanding at the mouth; as, a bell-mouthed gun.
--Byron.
Wiktionary
bell-mouthed
a. Expanding at the mouth.
Usage examples of "bell-mouthed".
Therefore that bell-mouthed barrel had been emitting a sound wave of high intensity that produced a total paralysis.