In intercultural communication, inappropriate linguistic forms are probably used due to the cultural difference which brings about the different criteria for the appropriateness in language use. The seemingly inappropriate language may violate the traditional pragmatic principle of appropriateness to a certain degree. However, Verschueren’s linguistic adaptation theory guides us to understand the probability of such phenomenon. This paper, on the basis of Verschueren’s adaptation theory, cites some so?called unidiomatic expressions to analyze the reason for their occurrence, and suggests some adaptation strategies in the seemingly inappropriate language use: mental adaptation, environmental adaptation and dynamic adaptation.