What does "gliss 2x" mean here?
I can just barely see the "common time" symbol at the left of your image, which denotes 4/4. The 2x is followed by parentheses which encapsulate the last rhythmic figure in the bar. This figure is an alternate version of playing beat 4 (otherwise the bar would have five beats in it).
This means, assuming there are repeats elsewhere in this excerpt, that the first time you play this measure, you play beat 4 as a quarter note with a gliss as indicated. The second time (2x), instead of playing that quarter note with gliss, you play the
s s e figure marked in parentheses. There is no gliss indicated on this figure.
Two seperate things. "Gliss" applies to the octave B in normal size notes. The smaller notes, in brackets, are to be played as an alternative on the second pass. We assume the section is repeated.