Certain legal terms are only capable of illustration and lack a precise definition. Definitions provide clarity but where the definition is not exhaustive there is uncertainty regarding its ambit. H.L.A Hart has attributed this indeterminacy to the ‘open texture’ of certain legal terminology. According to him, every term applies to a standard set of circumstances contemplated by the Legislator and in unforeseen situations giving rise to ‘hard cases’ the Court has to resolve this ambiguity. The first part of this paper analyses this aspect of Hart’s theory of open texture of language and delves into the criticisms put forth by scholars such as Dworkin and Fuller. The term good faith is used as an illustration to demonstrate the application of open texture of language. Good faith is a general principle of public international law and its meaning in the context of international trade law is the focus of this paper. An attempt has been made to analyse cases involving interpretation of good faith arising before the Dispute Settlement Body of the WTO using Hart’s interpretation of open texture of language to discern whether the theory finds application in the area of WTO law.