godan verb (-su)
stroke down; smooth down
Literally to stroke downward; most commonly used in the set phrase 胸を撫で下ろす (to feel relieved).
See also: 胸を撫で下ろす
母は子供の髪を優しく撫で下ろした。
The mother gently stroked down her child's hair.
I was relieved to hear that they were safe.