the GNU version of the Collaborative International Dictionary of English
n. One who, or that which, makes calm.
The Century Dictionary and Cyclopedia
n. One who or that which calms, or has the power to still and make quiet; one who or that which allays, pacifies, or soothes.
Word Usage
"Parental hyperconcern about safety and well-being turns a two-and-a-half-hour interlude of what once, in calmer days, may have been looked on as a break from the kids into a window of intense worry."