The headword, presumably extracted from the quotation given, is present participle (masculine nominative singular) of the verb e)kpagle/omai, for which see also epsilon 551.
The idea it conveys is one of been struck or hit by something. It is not always clear whether the reaction created through this feeling is positive (astonishment) or negative (amazement or fear). The present example, featuring Pyrrhus, and the second gloss provided at the end point to another meaning. Pyrrhus seems to have wanted to impress the Romans. So the verb is used here in the sense of taking a proud attitude, wanting to impress. A parallel passage is provided by the scholia to Euripides, Orestes 890), where it is explained as meaning to praise.
[1] Same quotation (but without the connecting ga/r) in ps.-Zonaras. Adler claimed it as coming from John of Antioch, but it is not recognized by Roberto. For Pyrrhus, King of Epirus 319-272, see generally pi 3232.