WordWeb Online

1. Spoken with poor articulation as if with a thick tongue
   "after a few drinks he was beginning to speak thickly"
    
2. In a concentrated manner
   "a thickly populated area";
   - densely
    
3. With a thick consistency
   "the blood was flowing thickly";
   - thick
    
4. With thickness; in a thick manner
   "spread 1/4 lb softened margarine or cooking fat fairly thickly all over the surface"; "we were visiting a small, thickly walled and lovely town with straggling outskirt"
    
5. In quick succession
   - thick

Antonym: thinly