extension phone(n = noun.artifact) extension, telephone extension - an additional telephone set that is connected to the same telephone line;
is a kind of phone, telephone, telephone set
cell phone, cellular phone, desk phone, dial phone, extension, extension agent, extension cord, extension course, extension ladder, extension service, file name extension, filename extension, mobile phone, orinasal phone, phone, phone bill, phone book, phone booth, phone call, phone card, phone company, phone cord, phone jack, phone line, phone message, phone number, phone plug, phone service, phone system, phone tapper, telephone extension, university extension