Piperidine is a cyclic amine. The piperidine skeleton is present in piperine, the main active chemical agent in pepper (Piper sp.), therefore the name.
It is also a byproduct of burning phencyclidine (PCP).
It is also found in marijuana.
Piperidine is often used for its mild basic properties, most notably in Fmoc-strategy solid phase peptide chemistry.