A process in which one determines the sex of a toad. A male toad will croak if squeezed behind the front legs, but a female will not. Toads can determine the sex of other toads in this way, and so can biologists.

If you spend any time hacking at MIT, you will see the phrase no toad sexing written in many places, almost as a sign-in. I have heard two explanations for this:
1. It became popular among some students to sneak up on each other and pinch under the arms, much like toads. This got annoying.
2. One hacker worked in a lab and had to sex toads. She was disgusted by it, and didn't want to go hacking and discover someone sexing toads in the middle of a machine room.
In either case, someone adopted no toad sexing as a sign-in, and, instead of writing a fake name or other identification upon reaching a difficult location, wrote no toad sexing. Others have taken up the cause, and there are also cases of no toed sexing and toad sexing allowed here written on the walls.
Toad sexing recently made an appearance as commandment 0x7 in the lobby 7 cathedral of the all night tool, Thou shalt not sex toads.