1. (of a body of water) free from disturbance by heavy waves

- a lake of tranquil blue water reflecting a tranquil blue sky

Similar word(s): calm, placid, quiet, smooth, still, unruffled

2. not agitated; without losing self-possession

- she became more tranquil

- tranquil life in the country

Similar word(s): composed, calm, serene, unagitated