Dictionary:

monoamine

  (mŏn'ō-ăm'ēn, -ə-mēn')

An amine compound containing one amino group, especially a compound that functions as a neurotransmitter.

An amine compound containing one amino group, especially a compound that functions as a neurotransmitter.

An amine containing only one amino group.

• m. oxidase — a cuproprotein enzyme that deaminates monoamines such as serotonin, epinephrine, norepinephrine, dopamine, tyramine and tryptamine. Called also MAO.
• m. oxidase inhibitors — substances that inhibit the activity of monoamine oxidase, increasing catecholamine and serotonin levels in the brain; they are used as antidepressants and antihypertensives. Called also MAO inhibitors.

The noun has one meaning:

Meaning #1: a molecule containing one amine group (especially one that is a neurotransmitter)