late 14c., of physical conditions, from arm (n.1) + -less. Meaning "without weapons" is attested from 1610s (from arm (n.2)), but that sense is more typically expressed by unarmed.
权威例句
1. A stool is a backless and armless seat.
凳子就是既没有靠背又没有扶手的椅子.
2. Liu, an armless pianist from Beijing, was named one of the show's finalists.