write down vs dash off

write down and dash off both are verbs.

Word	Noun	Adjective	Verb	Adverb
write down	No	No	Yes	No
dash off	No	No	Yes	No

As verbs, dash off is a hyponym of write down; that is, dash off is a word with a more specific, narrower meaning than write down:

Other hyponyms of write down include transcribe, notate, dash down, note, take down.

write down (verb)	dash off (verb)
reduce the estimated value of something	write down hastily
put down in writing; of texts, musical compositions, etc.	write quickly