Wasted Costs Order [WCO]:

is an order of a court that the plaintiff should pay the defendant's legal costs that were wasted by the legal proceeding initiated for an ulterior purpose other than the purpose of winning the legal point.

The best way to express the nature of a WCO is to quote the findings of  the case where one was found.  The court costs in a proceeding usually follow the case: the loser pays the costs of the winner.  A WCO can be ordered by that court, where one party has caused another party to expend resources needlessly, to defend an action initiated without any, or much, prospect of success, but merely, for instance, to defame the defending party so that they are forced to fight to clear their name.  The improper purpose of the plaintiff can be to merely buy time and to put the other party on the defensive and so at a disadvantage when suing the plaintiff.

One case where a WCO was found was in:

CABOOLTURE PARK SHOPPING CENTRE>> PTY LTD (IN LIQUIDATION) and WHITE INDUSTRIES (QLD) PTY LTD v. FLOWER AND HART (A FIRM) Nos. QG198 of 1986 and QG174 of 1992 FED No. 667 Courts - Practice and Procedure (1993) 117 ALR 253