A skreee is apparently an object relating to one's personal identity. The concept is common in the 26th century, though not in the 24th. In the 26th century, Mak Dav Al found his way to the skreee of Starfleet Captain Mak Dav Al, and thus terwelled him. This was considered a vile crime in this time period. (SCE short story: "An Easy Fast")