This is a jukugo word that uses the on'yomi readings of the kanji. You didn't learn this reading for 会 yet, so here's a mnemonic to help you:
When someone bows to you, you always feel a little uncomfortable, so you say, "Eh" (え) and try to get them to stop. You're so uncomfortable that you can't think of words and "eh" is all you can manage to get out.
You might have the decency to return my nod with a nod.