There are 2,115 words that start with O in AltF Lexicon. A word is in this list if its first letter is O. Single words only — multi-word phrases and compounds are browsable by letter but are not what someone asking this question means. The list is ordered by commonness — how often the word turns up in a large corpus of everyday English — then alphabetically, so the ones you already know come first.
Showing the 2,000 most common of 2,115 — ranked by how often each word appears in everyday English. The averages above describe those 2,000 words, not all 2,115.
Definitions come from Princeton's WordNet. Every word below the fold links to the same treatment — meaning, syllables, stress and pronunciation.
2,000 words, 200 to a page, most common first. The dots after each word are its commonness band.
The same letter, split by how many letters the word has.
Words and definitions come from Princeton University’s WordNet; commonness is measured against a corpus of everyday English. Full sources and licences.
Every word list