Violently forward, so as to strike something with one's face(adverb)
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Use "facefirst" in a sentence
"Treading water, he managed to shove her up onto the bank facefirst, her lower body still hanging into the river as he lifted himself out beside her."
"But Batista quickly pulled him off the top of the cage and introduced the champ facefirst into all four sides of the unforgiving steel."
"Jake got out the big brass key and turned the lock and the door to Room 14 opened and she thought she would faint right there, facefirst onto the bed."