To remove from a package or container, particularly with respect to items that had previously been arranged closely and securely in a pack.
They didn't have time to unpack their bags before going out to dinner.
To empty containers that had been packed.
They didn't have time to unpack before going to dinner.
To analyze a concept or a text.
(of a segment such as a vowel) To undergo separation of its features into distinct segments.
To decompress.
Having had its packing removed.
I worked all day and managed to get all the boxes unpacked.
Not yet packed.
The unpacked gifts are on the table.
(sometimes proscribed) Not yet having had its packing removed. (Especially after still. For more on this use, see http//itre.cis.upenn.edu/~myl/languagelog/archives/002171.html)
I left the box, still unpacked, at our old house.