1) hothouse effect 2) glasshouse effect 3) greenhouse effect an effect whereby infrared radiation, i.e. heat, emitted by a body that has absorbed energy from the sun, is trapped in a space enclosed by glass or other material that is largely opaque to infrared radiation greater than 2,5 ΒΌ (hence preventing radiant heat losses) but transparent to other incoming solar radiation. In a vacuum half of the energy absorbed is re-emitted towards the closed space GRM: n. (1,2,3)