post-it note

Wiktionary

1. n. A small piece of paper with an adhesive strip on one side.

GNU Webster's 1913

1. n. Trademark A small sheet of paper having the back part partly covered with a non-permanent gum which allows the note to be attached temporarily to another object, and easily removed without leaving any trace of glue on the object to which it was affixed. Such note papers are sold in pads of varying sizes.