someone beat me to it. non-reuptake inhibitor

it inhibits the "re-uptake" aka recycling aka taking neurotransmitters out of the synapse. inhibiting something that takes it out of the synapse, will increase its concentration in the synapse. so SNRIs increase the concentration of serotonin and norepinephrine at equilibrium conditions (takes a few weeks as complex systems of autoreceptors (receptors on the dendrite rather than axon) and receptors down/up-regulate)
so, you want to avoid serotonin syndrome or too much serotonin, and avoid overstimulation from norepinephrine, as well as any metabolic interferences. so stimulants may have their side effects exacerbated i think, as for other drugs, i don't know. i'm sure someone on BL knows though.. as far as psychedelics are concerned, phenylethylamine psychedelics are more stimulating than tryptamines for many, though i am not saying that you can't combine them--i don't know for sure either way. but i think stimulation could be increased. any psychedelic will invariably have some stimulating effects
all the tryptamines and phenylethylamines mostly act at certain serotonin receptors, namely, 5HT2A (primarily) and 5HT2C and 5HT1A, sometimes 5HT1D (eg psilocybin) (feel free to ask for articles, only reason i know these receptors is because i just wrote a paper on psych's), and as far as other receptors are concerned, depends on the psychedelic but each one will influence a different subset of 5HT receptors the most (hence why they vary individual to individual), with downstream effects on dopamine and other compounds
hopefully this little handful of pharmacology info will help someone figure all the interactions (however, it will be much more safe for you if you provide a list of what you may take with SNRIs, because no one can possibly account for every interaction). im pretty sure i remember reading on BL that taking an SSRI or SNRI will mute much of psychedelic effect, i've never taken SSRIs or SNRIs with psych's but i know there are many threads on bluelight about their interactions with psychs