care of (someone)
To the mailing address of someone. This phrase is typically written on a package or letter in cases when the intended recipient is only at someone's address temporarily or occasionally. You can just send my Christmas card care of my aunt because I'll be staying at her place for the holidays.
ˈcare of somebody
(American English also in ˈcare of somebody) used when writing to somebody at another person’s address: Write to me care of my sister, because I’ll be touring Africa for six months.This expression is usually written as ‘c/o’ on envelopes.