Interjection

1. Used in hesitant speech, or to express uncertainty; um, umm.

   She was going to, erm ... the salon.

2. Distinct from "um," (which generally indicates the speaker is searching for the proper word to use, or the thought to convey) "erm," typically intends to convey a distinct secondary message in a polite or subtle way, indicating something is incorrect about the current conversation, rather than there being some uncertainty about the subject. I.e. your question is inappropriate or I find you annoying or this is something you would know if you were paying any attention.

   Teresa says she's, erm, busy... (i.e. "Teresa doesn't want to talk to you.")

   That class was, erm, cancelled three weeks ago... ("Are you always on drugs, or was it just for this semester")