Abuse of process is a wrong or improper use of the process of a Court. Essentially, an abuse of process is using a court's process for a purpose or in a way that which is significantly different from the ordinary and proper use of the court's process: Attorney General v Barker  1 FLR 759.
Nature of Abuse of Process
A litigant is entitled to have its claim litigated provided that it is not frivolous, vexatious or an abuse of process. An abuse of process is an attempt to misuse the procedures made available by courts for an ulterior motive other than due legal process or otherwise in such a way that would be manifestly unfair to a party to the litigation. Courts exist as a final course for members of society to resolve disputes between them. Abuses are characterised by conduct which is manifestly unfair to a party to litigation or otherwise brings the administration of justice into disrepute. Courts maintain an inherent power to prevent abuses of process. Although a party to litigation may literally comply with the rules of court, does not prevent a party to the dispute being successful on a claim of such conduct.
In its widest sense, an abuse of process:
"extends to all categories of cases in which the processes and procedures of the court, which exist to administer justice with fairness and impartiality, may be converted into instruments of injustice or unfairness ... [P]roceedings before a court should be stayed as an abuse of process if, notwithstanding that the circumstances do not give rise to an estoppel, their continuance would be unjustifiably vexatious and oppressive for the reason that it is sought to litigate anew a case which had already been disposed of by earlier proceedings."
Examples of abuses of process include:
When a court decides that an abuse of process has taken place, it will strike out (on application by a party or of its own motion) either the entire statement of case or part, and may enter judgment of its own motion, should it appear that the innocent party is entitled. Courts have an inherent power to control its procedures. In addition, to these inherent powers, the Court may make a Civil Restraint Order preventing applications from being filed with the Court unless an application is first made to the Court to approve the application. Furthermore, a litigant who has been wrongly and maliciously sued may recover damages for civil malicious prosecution. Although not decided law, it is possible that the same principles may apply to defences.