interjection
Expression of hesitation, uncertainty or space filler in conversation.
(chiefly US) Dated spelling of mmm.
An expression to forcefully call attention to something wrong.
(childish) An expression of shocked disapproval used by a child who witnesses forbidden behavior.
verb
(intransitive) To make the um sound to express uncertainty or hesitancy.
noun
An occurrence of the interjection "um".
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.