\[NotReverseElement]
• Alias: !mem.
• Infix set relation operator.
• x y is by default interpreted as NotReverseElement[x, y].
• See Section 3.10.4.
• See also: \[ReverseElement] , \[NotElement] .
Usage
\[NotReverseElement] Notes
!mem. 
y is by default interpreted as NotReverseElement[x, y]. 
