An odd inequality sign

<
>
?

I would interpret that as "is not equal to".

 

Is it any of these?

[tex]\lessgtr, \quad
\gtrless,\quad
\lesseqgtr,\quad
\gtreqless,\quad
\lesseqqgtr,\quad
\gtreqqless[/tex]

 

I'd say it'd probably be the second one.

 

Again, my best guess is "is not equal to".

 

It's an abbreviation of < or >, the alternatives being explained or elaborated on nearby.

You could write: a≶b≶c, which means that either a<b<c or a>b>c.
Or you could write something like: |x|=±x if x≷0.
The upper level is one case, the lower level is the other case.

It is rarely used. Different cases are usually put on different lines with braced conditions.