untheatricadj.
Etymology: Previous versions of the OED give the stress as: untheˈatric.
the world > action or operation > behaviour > unaffectedness or naturalness > [adjective]
1858 E. Bulwer-Lytton i. ix The cobbler yielded to the impulse of an untheatric man.
This entry has not yet been fully updated (first published 1926; most recently modified version published online June 2020).