From Longman Dictionary of Contemporary Englishnail somebody/something ↔ down phrasal verb informal1 DECIDEto reach a final and definite agreement or decision about something Two days isn’t enough time to nail down the details of an agreement.2 TELL/ORDER somebody TO DO something nail somebody down to force someone to say clearly what they want or what they intend to donail somebody down to Before they repair the car, nail them down to a price. → nail→ See Verb tableFrom Longman Business Dictionarynail down phrasal verb [transitive]1 nail somebody down informal to force someone to say exactly what they want or what they intend to donail somebody down to somethingBefore they repair the car, nail them down to a price.2 nail something → down American English journalism to reach a final and definite decision about somethingThe US wants to nail down an agreement on anti-subsidy rules.3 nail something → down American English journalism to make certain that you will get somethingThe prospect of a shortage has U.S. companies rushing to nail down long-term supplies of critical parts.He sold the shares just because he thought it prudent to nail down a profit. → nail→ See Verb table
