intj

• (chiefly US) Dated spelling of mmm.
  ""About the same, wherever you go," he agreed. "Um," I said."
• (childish) An expression of shocked disapproval used by a child who witnesses forbidden behavior.
  "While I was in her room, Sam walked by and said, “Um, I'm telling!” “You're telling what?” I asked. “You're reading Tori's journal,” she said."

verb

• (intransitive) To make the um sound to express uncertainty or hesitancy.
  "Meanwhile, in the popular mind umming was simply a bad habit, akin to spitting or picking one’s nose."

particle

• (dated, sometimes humorous, often offensive) An undifferentiated determiner or article; a miscellaneous linking word, or filler with nonspecific meaning; representation of broken English stereotypically or comically attributed to Native Americans.
  "Me be Injun. Him um Growling Bear. Him um heap big chief."

noun

• (philately) Initialism of unmounted mint.