| An orchestra tunes to one | 25 |
| An orb-weaving spider with black markings resembling a mustache was named after this musician | 93 |
| An orb or god | 13 |
| An orator's may rise and fall | 33 |
| An orangutan | 12 |
| An orange, minus the juice | 26 |
| An opposite of to | 17 |
| An opposite of down | 19 |
| An opponent of | 14 |
| An ophidian | 11 |
| An operator may help place one | 30 |
| An operator may call on one | 27 |
| An operative | 12 |
| An operatic plant? | 18 |
| An opening line | 15 |
| An OPEC land | 12 |
| An op-ed has one | 16 |
| An Onassis, for short | 21 |
| An Onassis nickname | 19 |
| An Onassis | 10 |
| An omen might do it well | 24 |
| An omega stands for it | 22 |
| An Olympics star in 1936 | 24 |
| An Olympics site: 1988 | 22 |
| An Olympic twin | 15 |
| An Olympic team | 15 |
| An Olympic swimming champ: 1932 | 31 |
| An Olympic swimmer needs a big one | 34 |
| An Olympic swimmer may have a long one | 38 |
| An Olympic ring | 15 |
| An Olympic medal | 16 |
| An Olympian may thrust it | 25 |
| An Olympian | 11 |
| An Olivier co-star: 1939 | 24 |
| An olive is one | 15 |
| An oleoresin | 12 |
| An older one may be beaten | 26 |
| An older brother of Seth | 24 |
| An old-timer | 12 |
| An old Warner Bros. production? | 31 |
| An old tongue | 13 |
| An old tire, perhaps | 20 |
| An old syllable meaning "before" | 42 |
| An old story from Paul? | 23 |
| An old story | 12 |
| An old secretary might sit in one | 33 |
| An old ruse: Colloq. | 20 |
| An old one may need a key | 25 |
| An old master | 13 |
| An Old Glory color | 18 |
| An old glory | 12 |
| An old flame's pastime? | 27 |
| An old couple fell in it | 24 |
| An old Burmese capital | 22 |
| An Okla. native | 15 |
| An OK city? | 11 |
| An OK city | 10 |
| An ointment | 11 |
| An oily hydrocarbon | 19 |
| An oilman | 9 |
| An oil source | 13 |
| An oil producer | 15 |
| An oil man | 10 |
| An offspring of Juno | 20 |
| An official under Nero | 22 |
| An official language of the Northwest Territories | 49 |
| An official language of Sri Lanka | 33 |
| An official language of Singapore | 33 |
| An official language of Pakistan | 32 |
| An official lang. of Tonga | 26 |
| An official lang. of Switzerland | 32 |
| An official lang. of Malta | 26 |
| An official lang. of Kenya | 26 |
| An official lang. of Hong Kong | 30 |
| An official enforces it | 23 |
| An officer to avoid like the plague? | 36 |
| An officer below a lt. | 22 |
| An officer and a gentleman? | 27 |
| An offer to "en1arge your m@nhood," probably | 54 |
| An off-ramp may lead to one | 27 |
| An oenophile might detect a hint of this | 40 |
| An octopus' eight | 21 |
| An octopus has eight | 20 |
| An October birthstone | 21 |
| An octahedron has twelve | 24 |
| An ocelot has lots | 18 |
| An ocean: Abbr. | 15 |
| An ocean look? | 14 |
| An oc. | 6 |
| An obviously angry snake or cat | 31 |
| An observation game and an old TV series | 40 |
| An oboe, perhaps? | 17 |
| An oboe has two | 15 |
| An obnoxious person | 19 |
| An objet d'art | 18 |
| An objective of NOW | 19 |
| An objective for Sally? | 23 |
| An object of Bohr's research | 32 |
| An obese Lugosi? | 16 |
| An Obama girl | 13 |