I'd like to segment subscribers with OR criteria. For example, I'd like to have those with last name AAA and those with last name BBB in one segment. Is it possible? The multiple criteria seems to be just layering criteria, thus AND condition, not OR condition.
Donna is absolutely right! In order to access that option, be sure to click "add" in between adding searching criteria instead of clicking "done." You'll want to click "done" at the very end, after you've added all of you OR criteria.
Give that a shot and let me know if you need more help!