experimenter

Concise Oxford English Dictionary © 2008 Oxford University Press:
experiment/ɪkˈsperɪmənt/

▶noun

• 1 a scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact.

• 2 a course of action tentatively adopted without being sure of the outcome.

▶verb

• 1 perform a scientific experiment.

• 2 try out new things.

– derivatives
experimentation noun,
experimenter noun.

– origin ME: from OFr., or from L. experimentum, from experiri ‘try’; cf. experience and expert.