1.
Obnoxious: objectionable, offensive, annoying
2.
Obscure: not clear or plain
3.
Obstacle: something that slows or stops progress
4.
Occasion: a special or important time, event, or celebration
5.
Occasionally: from time to time
6.
Occur: to happen, take place
7.
Odor: a sensation perceived by the sense of smell; scent
8.
Offense: a violation or breaking of a social or moral rule
9.
Oneself: a person's self
10.
Opossum: animal, marsupial
11.
Opponent: a person who is on an opposing side in a game, contest, or controversy
12.
Optimism: tendency to look on the more favorable side of events or conditions and to expect the most favorable outcome
13.
Organization: the act or process of organizing
14.
Organize: to arrange methodically or in order
15.
Pageant: a show or exhibition, especially one consisting of a succession of participants or events
16.
Pamphlet: a complete publication of generally less than 80 pages together and usually having a paper cover
17.
Parse: to play a specified role in the structure of a sentence
18.
Particular: of or pertaining to a single or specific person, thing, group, class, etc.
19.
Persist: to continue steadfastly or firmly
20.
Persuade: to cause to believe; convince