(1) A powerful insect repellent.
(2) The active ingredient used in many insect repellents to keep away biting insects like mosquitoes and ticks. Its chemical name is n, n-diethyl-meta-toluamide, and that's exactly how it tastes.
(3) The mythical chemical substance that hikers think will save them from mosquitoes and other tiny nipping predators.
Dieter tried DEET, liked it, and became a DEETer. It kept the bugs away, or would have if he had rubbed it on his skin and hadn't swallowed it. Poor Dieter, now DEET-ceased.