button
Pronunciation: /ˈbʌt(ə)n/
noun
- 1a small disc or knob sewn on to a garment, either to fasten it by being pushed through a slit made for the purpose or for decoration.
- a small round object resembling a button: chocolate buttons
- Fencing a knob fitted to the point of a foil to make it harmless.
- used in reference to things of little worth: he will never give away anything that is worth a button
verb

Phrases
-
button one's lip
- informal stop or refrain from talking.
-
on the button
informal, chiefly US - punctually: we arrived at 5.20 on the button
- exactly right: the programme is right on the button every time
-
press the button
- informal initiate an action or train of events (often used to refer to the ease with which a nuclear war might be started).
-
push (or press) someone's buttons
- informal arouse or provoke a reaction in someone: don’t allow co-workers to push your buttons
Phrasal Verbs

Origin:
Middle English: from Old French bouton, of Germanic origin and related to butt1