answering machine; voicemail
Abbreviation of 留守番電話. Refers to the device or the voicemail system itself.
See also: 留守番電話
留守電にメッセージを残しておいたよ。
I left a message on your answering machine.
電話に出られなかったら、留守電に切り替わります。
If I can't answer the phone, it will switch to voicemail.
留守電 is the casual abbreviation used in everyday speech, while 留守番電話 is the full, more formal term for the same device or service.
Abbreviation of 留守番電話 (るすばんでんわ), literally 'absence-duty telephone'.