I've been using and teaching Unified Modeling Language (UML®) and Systems Modeling Language v1 (SysML®) for a long time. The hardest thing about teaching them is trying to pronounce 'Guillemets' when describing the special quote symbols used around stereotype keywords.Before trying to pronounce it, notice that it is often written with a capital Guillemet because:
Guillemet is a diminutive of the French name Guillaume (equivalent to English William) ...
The singular Guillemet refers to either of the sideways double chevrons « » used in UML and SysML to indicate a stereotypes «keyword». The plural Guillemets refers to the pair.
So how is it pronounced in English? Or better asked, how would you like to pronounce it, because if you ask Dr Google you'll find so many different authoritative pronunciations it hardly matters.
If you are feeling more French with your 'll' and don't wish to pronounce the final 't', go for /gē-(y)ə-'mā/, as demonstrated here. Confusingly, that same video also indicates that /gi-lə-'met/ with very English 'll' and 't' is valid, but does not pronounce it that way.
This one pronounces both the 'll' and final 't' but not the 'e' after the 'll'.
There's another attempt here that sounds like a robot that has never visited France.
The Cambridge Dictionary seems to indicate that in British English the the 'll' is pronounced but in American English it is not, and in both cases the 'e' after the 'll' is ignored and the final 't' is silent.
Maybe it's just easier to pronounce 'pronunciation'.