1. Not able to be counted (e.g. because too many to count) 
2. (grammar) of a word that does not have a plural form

Encyclopedia: Uncountable

• overheated
• overheating
• overindulge
• overindulgence
• overindulgent
• overinflated
• overjealous
• overjoy
• overjoyed
• overkill
• overladen
• overland
• overlap
• overlapping
• overlarge
• overlay
• overlayer
• overleaf
• overleap
• overlie
• overlip
• overload
• overloaded
• overlong
• metalhead