De or het expertmeeting?

The correct Dutch article is:

de expertmeeting

Rule Words ending in -ing: almost always de. See the rule

How to use expertmeeting

the expertmeetingde expertmeeting
this expertmeetingdeze expertmeeting
that expertmeetingdie expertmeeting
our expertmeetingonze expertmeeting
your expertmeetingjouw expertmeeting
every expertmeetingelke expertmeeting
which expertmeeting?welke expertmeeting?
a big expertmeeting / the big expertmeetingeen grote expertmeeting, de grote expertmeeting