There is a very interesting approach on the meaning of "experimental" in typography in
We Want You To Love Type. The essay is by Peter Bil'ak and it's called "Experimental Typography. Whatever that means".

George Triantafyllakos - backpacker.gr

See also "Experiments in Type Design," by Tobias Frere-Jones. Texts on Type: Critical Writings on Typography, edited by Steven Heller and Philip B. Meggs. Allworth Press, 2001.

I’m in a process of writing my thesis on Typographic Space. I have been struggling to clearly define the meaning of ‘experimental typography’.

Ana, I'm confused by your statement -- what is the relationship between typographic space and experimental typography?

Ricardo - In my thesis, I am stating that the use of space in typograohic design by their very nature are dependent on and defined by convetions. I also state that these common patterns have inspired me to use experimental typography in my practical work in order to investigate the use of space in typographic layouts. Now, I need to clearly state what I mean by 'typographic experiment'. There are a lot of definitions made by a lot of designs but none seem to be clear or defined.

ana.

[ I would say ] :: 'experimental typography' is the process creating letterforms for the sake of the form itself — not for the purpose of expression or legibility, but for the sole reason of interpreting the alphabetic symbol as a shape with infinite possibilities of positive and negative space.

That's just my opinion (in a run-on sentence).

Good luck with your thesis!