Examples of uncommon English words that begin with "o" include "obeliscolychny," "oast," "oblocutor," "obvolvent," "olfactible" and "oligomania." Additional uncommon words beginning with this letter include "ololygmancy," "ommateum," "outrecuidance" and "ozostomia."
The word "obeliscolychny" refers to a lighthouse using the same morpheme as the word obelisk, which refers to a monument that is physically similar in stature to a lighthouse. The word "oast" refers to a specific type of kiln that is used to dry hops or malt; this type of kiln is used in the production of certain beers. An oblocutor is a person who denies or disputes something.
An object is obvolvent when it wraps around another object while curving downward or inward. An olfactible object is one that can be smelled. Oligomania, using the same morpheme as oligarchy and oligochrome, refers to an obsession focused on a select few thoughts or ideas.
Ololygmancy is the process of telling fortunes or divining spiritual information by listening to the howling of dogs. Ommateum is a medical term that refers to the compound eye common to many insects. Outrecuidence is a mode of behavior that is overwhelmingly arrogant. Ozostomia is an uncommon word that refers to bad breath; it derives from the Greek word ozostomos.