Superlative form of ghostly: most ghostly.(adjective)
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Use "ghostliest" in a sentence
"The one thing that fits those specifications is a black hole, an object so massive and hence so gravitationally powerful that not even the ghostliest ray of light can escape its clench."
"I imparted my secret to him, because I had never quite forgotten his throwing his cap at the bell; because I had, on another occasion, noticed something very like a fur cap, lying not far from the bell, one night when it had burst out ringing; and because I had remarked that we were at our ghostliest whenever he came up in the evening to comfort the servants."
"It was as if all the ghosts in Hades had suddenly piped up at their shrillest and ghostliest."