Synonym of VISCOUS:

• Viscous (adjective):
English Meaning: (of a liquid) Thick and sticky; not flowing easily.
Bangla Meaning: আঠালো; চটচটে।

Synonyms: sticky, viscid, turbid, Gluey, Tacky, Pasty, Syrupy, Gummy.
Antonyms: Watery, Thin, Dry, Melted, Soupy.

Example Sentence: 
1. The honey is much thicker and more viscous, and it pours very slowly compared with the water.
2. If the lava is very viscous, and there is a great deal of gas present, pumice is formed.

Source:
1. Accessible Dictionary.
2. Cambridge Dictionary.
3. Merriam-webster Dictionary.