Surely this word appears in your dictionary.
But we should look for it in the singular masculine form: לְשׁוֹנִי, that means linguistic (male). We have here the feminine singular because it qualifies the preceding noun בְּחִינָה which is, as we saw, a feminine noun.
One may also think of ל being the well known preposition that means to, for. But this is not the case.
We thus get linguistic (female).