um

Short definition from Wiktionary

Interjection

1. 1
   Expression of hesitation, uncertainty or space filler in conversation.
2. 2
   Dated spelling of mmm.
3. 3
   An expression to forcefully call attention to something wrong.
4. 4
   An expression of shocked disapproval used by a child who witnesses forbidden behavior.

Verb

1. 1
   To make the um sound to express uncertainty or hesitancy.

Noun

1. 1
   An occurrence of the interjection "um".
2. 2
   Initialism of unmounted mint.

Particle

1. 1
   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.

Proper noun

1. 1
   Initialism of University of Miami.
2. 2
   Initialism of University of Michigan.
3. 3
   A surname from Korean.