Scarf down is an informal phrasal verb meaning “eat something quickly and eagerly.” It’s typically followed by a noun or noun phrase (e.g., “I watched him scarf down two burgers”).
The simple past tense and past participle of the verb “scarf” is “scarfed” (e.g., “I scarfed down my lunch”).
Scarf can also be used as a noun to refer to an item of clothing (the plural of which is scarves or scarfs).
The QuillBot Grammar Checker can help ensure you’re using phrases like “scarfed down” correctly.