This is the 506th most frequent Persian word.
تر
"تر" means "wet" in English.
Here, "تر" is used to describe a state of humidity or wetness.
آب و هوای شمال خیلی تر است.
The northern climate is very humid.
The word "تر" is used as a comparative suffix to indicate 'more', in this case, 'wetter'.
این حوله از حولهی قبلی تر است.
This towel is wetter than the previous towel.
In this usage, "تر" conveys the idea of retaining some degree of wetness, used in a descriptive sense.