Minus to you for not checking more.http://encarta.msn.com/dictionary_18616 ... aught.html
on·slaught (plural on·slaughts)
The again Wikitionary has the plural for cat, but not onslaught.
http://en.wiktionary.org/wiki/cat
http://en.wiktionary.org/wiki/onslaught
And SHEEPS redirect to sheep, and it isn't the plural either: http://www.thefreedictionary.com/sheeps
If my word is out then i'll go with:
tsi - http://en.wiktionary.org/wiki/tsi