This is the 3903rd most frequent Dutch word.
vlooien
"Vlooien" means "to flea" (removing fleas) or "fleas" (plural of flea).
Here, 'vlooien' refers to the noun 'fleas', indicating the small insect.
De hond zat vol met vlooien.
The dog was full of fleas.
In this case, 'vlooien' is used as a verb, meaning 'to remove fleas from'.
Ik zag hem zorgvuldig zijn jas vlooien.
I saw him meticulously flea-comb his coat.
Here, 'vlooien' refers to a traditional table-top game known as 'flea jumping'.