1) At ease 2) At peace 3) Calm 4) Calming 5) Composed 6) Irenic 7) Motionless 8) Peaceable 9) Peaceful 10) Placid 11) Quiet 12) Restful 13) Sedate 14) Serene 15) Still 1) Calm 2) Comfortable 3) Composed 4) Cool 5) Cosy 6) Dog keeping new queen calm 7) French word used in English 8) Hassle-free 9) Not agitated 10) Peaceful 11) Quiet 12) Relaxed 13) Relaxing 14) Serene 15) Still 16) Stress-free 17) Undisturbed 18) Unperturbed 19) Unruffled 
• (a.) Quiet; calm; undisturbed; peaceful; not agitated; as, the atmosphere is tranquil; the condition of the country is tranquil.
tranquil Peaceful, quiet, calm. Formed from trans-, 'through, across' and quies, 'rest, quiet'.
peaceful
not agitated