People I meet for the first time (or relatives or friends I meet after a long time) naturally ask me what I do with my life. I mumble something incoherently about a PhD. They ask me "in what". I say "Molecular Pharmacology". I'm usually greeted with blank stares, or a "what's that?".
I go on to explain that Pharmacology is the study of the interaction of living cells and organisms with the molecules they encounter in their environment. Modern molecular pharmacology looks at these aspects at a molecular level, by which we can understand specific pathways in systems that are affected. I talk about how we use basic biochemistry, molecular biology, cell biology, genetics and so on to investigate pathways that could serve as potential drug targets, and also study the effects of drugs on these target pathways.
After this long winded explanation, the person listening to me nods understandingly, and sympathetically, and usually replies:
"Ah! So, you're a Pharmacist!!"
One of my collegues puts it across nicely. He says that calling a Pharmacologist a Pharmacist is just like walking up to a doctor, and asking her if she's the nurse.