(of a body of water) free from disturbance by heavy waves
A ribbon of sand between the angry sea and the placid bay. The quiet waters of a lagoon. A lake of tranquil blue water reflecting a tranquil blue sky. A smooth channel crossing. Scarcely a ripple on the still water. Unruffled water.
source: WordNet 3.0
not easily irritated
An equable temper. Not everyone shared his placid temperament. Remained placid despite the repeated delays.
