drop-in

drop-in汉语翻译：
【计】 冒"1"; 混入信息英语解释：
动词 drop-in:

visit informally and spontaneously同义词：drop by, drop in, come by

详细解释：
drop-in
n.（名词）
One who casually drops in, as to visit or obtain an appointment.
不速之客：偶然来访或订约会的人
An informal social event.
非正式社交聚会