From Wiktionary, the free dictionary
From non- + expression.
nonexpression (countable and uncountable, plural nonexpressions)
- Absence of emotional expression.
2007 October 2, Kent Sepkowitz, M.D., “Behind the Doctors’ Mask, a Little Room to Maneuver”, in New York Times[1]:
Everyone who visits now has the same inscrutable nonexpression.
- That which is not a logical or mathematical expression.