(formal, possessive) Of whomever; belonging or related to whichever person or persons; whoever's.
Whosever sunglasses these are will have to pick them up tomorrow.
"And she is not wholesome, whosever word it was. She was there, hanging about him when he was so bad, before the worst came." 1866, Mark Twain, The Galaxy, W.C and F.P. Church, page 584:
(formal, possessive) That of whomever; that which belongs or is related to whatever person or persons; whoever's.
At first she had been only relieved to find that the voice, whosever it was, trickling over the wire, was not his. 1930, Margaret Ayer Barnes, Years of Grace, Part III, Chapter III, page 303:
He can only play whosever on the other side of the net. 2004 September 12, Storm, “Will Hewitt Make Tennis Slam History Tomorrow?”, in rec.sport.tennis (Usenet):
Don't worry. I'm gonna find whosever responsible. 2013 October 11, Joshua Hamilton, “The Sting” (6:17 from the start), in Ian Graham, director, The Legend of Korra, season 2, episode 6, spoken by Mako (David Faustino):
This would make J. Dumars come off the bench and sometimes give us a nice 3 guard line-up sometimes with Hunter at SG, Dumars at SF, and whosever in between the pg's from GS. 1997 January 7, Raj Capoor, “S. Augmon wants out cont'd”, in alt.sports.basketball.nba.det-pistons (Usenet):
People keep passing the buck to whosever left to blame. 2000 July 20, Michael J. Sacks, “It's started already”, in alt.sports.baseball.chicago-cubs (Usenet):