The infliction of trouble or distress.
"The troubling news from the hospital left everyone in a state of deep distress."
present participle of trouble
"The troubling noise coming from the engine made me worry that we might break down on the highway."
causing distress or worry or anxiety
"distressing (or disturbing) news"
"lived in heroic if something distressful isolation"
"a disturbing amount of crime"
"a revelation that was most perturbing"
"a new and troubling thought"
"in a particularly worrisome predicament"
"a worrying situation"
"a worrying time"
distressing, worrying
"The sudden silence from his phone left me feeling deeply troubling about where he might be."