A room in which persons assemble, especially for dancing. See assembly.(noun)
The Century Dictionary (Public Domain)
Use "assembly-room" in a sentence
"“In private? and in an assembly-room? — he must be mad — Tell him to call upon me tomorrow morning.”"
"From the time of his first boyish gallantry, on the ill-fated birth-day of Camilla, Indiana had never so much struck young Mandlebert, as while he attended her up the assembly-room."
"The soldier who enters the field of battle requires not more courage, though of a different nature, than the faded beauty who enters an assembly-room."