The annoying habit whereby someone leaves you the same voicemail message on more than one of your phones (i.e. your cell and your home; your work and your cell; etc.) and then you have to listen through the exact same message twice.
Most people have a friend or family member who has this habit and those people are known as double messagers.
Dude, Nick double messaged me on my cell and at home! He bugs.
Mike is such a double messager. Doesn't he know I already got the first message?
After ignoring a facebook message/text from a playa tryin' to "get with you", they proceed to send a second (or even THIRD) message.
Which you again ignore.
Playa:"lets hang out"
Playa:"whats your number?"
Playa:"we need to chill"
this ^ is a double message.