The sign for "microwave" is very similar to signs based on
the concept of "light." The "microwave" sign basically shows the
microwaves being broadcast from the sides into the food in the middle.
Sample sentence: "Do you prefer to use the stove or a microwave?"
= YOU FAVORITE STOVE [bodyshift] MICROWAVE, WHICH?
Some people just spell "MW."
A cute joke sign I've seen for the sign "microwave" is to "wave" the tip of your
pinkie up and down by flexing it at the smaller two knuckles. Geddit? A
"micro" wave. (Ahem.)