I’ve noticed that teenage and twenty-something women often put a cushion on their laps when sitting down. I don’t think I’ve ever seen a man or an elderly woman do this.
Why do they do it?
To hide their erections.
I’m sorry, I haven’t a clue.
To hide their bellies. Tween/teen girls are very self-conscious about their tummies bulging out when they bend their waists to sit. Also spreading thighs is a huge concern; when you sit they spread out on the chair in an unappealing manner.
There’s also the possible issue of wearing a skirt or short shorts that would be too revealing if they sat in the various contortionist positions which also become extremely important at this age. The cushion allows them to perch indian-style on a high bar stool in a mini-skirt without flashing the room.
Mornington Crescent.
I’m an elderly fat man. Do you think this would be appropriate for me? (And do they make cushions in my size?)
No. Elderly fat men should not wear mini-skirts after age 35. Sorry.
Even after Labor Day?
What if it’s to hide my erection?
If you are an elderly fat man and still getting uncontrolled erections you need to either time the Cialis better or just let it proudly wave in the wind!
Ha! I first heard of Mornington Crescent a few years ago here. My first thought was that it was the female equivalent of morning wood. 
.
I’m not sure a mini skirt will hide an erection. Unless it’s very small. (The erection, that is.)
NB I’m not speaking from personal experience. Honest.
Only on the Straight Dope could someone find a link from Mornington Crescent to sexual arousal. (Without going via Belsize Park first.)
Was there a dog in the room?
Me too, especially in the context above. Was thiiis close to making a mental note for future use when your post saved me.
So it doesn’t mean that. I’m disappointed, and don’t really care to know what it actually does mean now.
FYI, morning wood in Japanese is 朝立(asa-dachi), which, in addition to more prosaic meanings, also literally brings together the kanji for “morning” and “stand.”
Who knows, it might come up (rimshot!) in a pub contest or somet.
For some of them it’s just something to have in their hands and play with it nervously in a way that’s relatively discreet. Once they relax, they just plop it at their side.
I still do so, sometimes (and it’s been a bit since I was a teen). Usually, it’s either to just get them out of the way of my seat if I’m at someone’s home, or because I’m cold in that seat. If a person has some decorative pillows on their couch, and the couch is near or under an A/C vent, chances are high that I’ll have that pillow on my lap upon sitting down.
“I’m telling everybody!”
I sometimes do it, but usually it’s just because I like something to cuddle with. It’s definitely nothing to do with a bulgy tummy because my tummy is very tiny.
What the hell are you people talking about? People put cushions on their laps? Hiding bellies? What? So people are just carrying around cushions with them? Like on the bus? At work?
If you need something to cuddle with, check under my skirt.