How many words start with OO?

10, from 5 letters up to 5. All of them are on this page.

What is the highest scoring word that start with OO?

OOZED at 15 points in Scrabble, and OOZED at 15 in Words With Friends, because the two games score the tiles differently.

OOBIT, OOHED, OOMPH, OONTS, OOPED, OORIE, OOSES, OOTID, OOZED, OOZES.

10 of them: OOBIT, OOHED, OOMPH, OONTS, OOPED, OORIE, OOSES, OOTID, OOZED, OOZES.

There are 10 of them. The highest scoring is OOZED at 15 points in Scrabble, and the set averages 8.6.

Most common words first, then the rest A to Z.

The most familiar words on this page and what they mean. Tap any word for its full entry, score and anagrams.

OOHED verb form of OOH: express admiration and pleasure by uttering ‘ooh’ or ‘aah’
OOTID noun mature ovum after penetration by sperm but before the formation of a zygote
OOZED noun form of OOZE: any thick, viscous matter
OOZES noun form of OOZE: any thick, viscous matter

Definitions from Open English WordNet, CC BY 4.0.

All of them: Word lists.