Gut-ripping is the technique in which a robot gets up underneath another robot, (most of the time by means of a wedge) and damages their underside, which is commonly unprotected. Most of the time, it's an efficient technique, although it can't handle all scenarios like fighting specialized bots like Mome Rath.
A good gut-ripper needs a wedge and a good drive train to get under the opponent quickly.
It is possible to resist Gut-ripping by mounting Half sheets of titanium directly to the underside of you baseplate( in DSL) or by using belly Caster armor (in Stock).
When playing online, it is best to stop Gut-ripping and back off after a while to see if you opponent can still move, or else it will begin to resemble pinning.