The paper aims at exploring some of the conditions and ways in which LSP(Language for Special Purposes) adult learners perceive misleading vocabulary. Specifically, the paper represents an attempt to find out whether adult learners of English who know the meaning of certain words can or cannot work out the new meaning of phrases or collocation which would result from the combination of two or more words. on top of this, we will try to give reasons for the learners’ inaccurate guesses. The phrases and/or collocations used in this study were contextualised in sentences to show or mirror our learners’ ability in working out their collocational new meanings. To achieve this objective, two methods were followed. First, individual general words (not technical) were taught and then a combination of two or more of these words (to give specific meanings) was worked out by 80 LSP learners through context. Second, after testing the same learners in these words and grading their responses, both descriptive and inferential statistics were used to indicate both frequencies and statistical significance levels. The samples and teaching situation were taken from the Jordan University of Science and Technology. The study showed that JUST learners found difficulties in working out or guessing the specific meanings of phrases and collocations when combined to form new meanings though they knew the meaning of each word individually. These phrases look deceptively easy to our Arabic speaking LSP learners at first sight, but their meanings can be radically different from what our learners might expect. The study ends up with a number of practical teaching implications including paraphrasing and idiomaticity in the first place. Finally, some other research recommendations were suggested.