Using 'scrooge' implies a strong negative judgment towards someone's generosity. Don't be a scrooge; help fund the school play.
Pro Tip 2/3
Holiday Reference
'Scrooge' is often used more around Christmas time due to its association with the character from 'A Christmas Carol'. My uncle turns into a real scrooge every December.
Pro Tip 3/3
Colloquial Usage
Best used in informal situations; might be too casual or disrespectful in formal contexts. My friend joked about being a scrooge when splitting the bill.