• toss something back | toss something down: ~을 원샷하다, 원샷 때리다. | bottoms

• toss something back | toss something down
-to drink something very quickly, especially alcohol - Oxford Phrasal Verbs Dictionary for Learners of English
-To eat or drink something very quickly or voraciously /vəˈreɪʃəsli/. A noun or pronoun can be used between "toss" and "down." - 프리
-To drink something very quickly or in one swig, especially an alcoholic beverage. A noun or pronoun can be used between "toss" and "back." - 프리
-Slang. To drink something quickly, especially in one draft by suddenly tilting - 프리
e.g.)
She tossed back glass after glass of champagne. (Oxford)
He tossed back the rest of his drink and walked out. (Oxford)
I tossed down the meal as quickly as I could so I could get back on the road. (프리)
After losing his job, he sat at the bar tossing drinks down all night. (프리)
You're going to suffer for it tomorrow if you keep tossing down shots like that. (프리)
I'm not surprised you feel so horrible, judging by the way you were tossing back drinks last night. (프리)
Let me just toss this soda back, and I'll be ready to go. (프리)
The bartender tossed back a shot of whiskey. (프리)
I tossed my coffee back and left the restaurant. (프리)

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• bottoms up!
-(informal) used to express good wishes when drinking alcohol, or to tell somebody to finish their drink
: 건배!; 쭉 마셔[원 샷]!