This paper is about the semantics of one of the Oromo adposition of verticality, namely irra,rn'on/over'. In cognitive linguistics it is argued that lexical items exhibit category of meaningrnwhereby a single lexic al item can have a primary meaning which gives rise to various extendedrnmea nings. This meaning extension is obtained by the virtue of Conceptual Metaphor.rnWith the assumption th at meaning is encyclopaedic instead of dictionaric, and words arernpol ysemic by nature, it has been discussed that this Oromo adposition yields a number ofrnmetaphorical meanings which result from the primary spat ial senses. Data obtained fromrnintrospection supplemented with elic itation have been anal yzed and it has been found that irra asrnits primary sense des ignates a trajector located higher than a landmark in contact or withoutrncontact with each other. And in the case of the absence of contact between a trajector and arnlandmark, the trajector is conceived to be within the potential reach or sphere of influence of thernlandmark. From this primary spatial meaning of the adposition, various extended meanings havernbeen systematically deri ved in li ght of the Theory of Conceptual Metaphor.rnThus, it has been shown that the Oromo postposition irra is a highly polysemous lexi cal i' em.rnFrom primary meaning of relat ing a trajector located higher than a landmark, a number of abstrac trnmetaphorically ex tended senses can be systematically deri ved from the proto-scene.