Doodad informal noun
Used to indicate a name of gadget or item whose true name is unknown or has been forgotten.
A: Give me that doodad to fix my car. B: Here you go.
Is this the little doodad you lost, Mark?
I'm afraid that we can't afford to buy that doodad.
To do domething based on your emotions rather than for rational reasons
I can't believe that Tom beat his classmate. He's always the one who let his heart rule his head.