MILEY TO MATT LAUER PEOPLE STOP BANGIN' AT 40 ... And You're way past 40

http://www.tmz.com/videos/0_onx5nsf8

Miley Cyrus just told Matt Lauer she'll probably stop being so sexual when she turns 40 ... because that's the age when people STOP having sex. 

Miley appeared on the "Today" show this morning -- in a pair of really short shorts -- when Matt asked if Miley's hyper "sexual side" is just a phase or something she expects to grow out of? 

Miley replied with a pretty direct shot at Lauer ... a shot he didn't really seem to get at first. 

Best part of the exchange ... Matt reveals his age (way older than 40) ... and Miley says, "Then you're really definitely not sexual."

Still, we gotta ask ...