| obligate |
to bind legally or morally; constrain. [3 definitions] |
| obligation |
the act of binding oneself legally or morally to do or to refrain from doing something; contract. [5 definitions] |
| oblige |
to cause to feel bound to do something or to act in a certain way. [4 definitions] |
| obliging |
ready to help or do favors for. |
| oblique angle |
any angle that is not a right angle; acute or obtuse angle. |
| oblong |
having one dimension longer than the other, as in a rectangle or ellipse; elongated. [2 definitions] |
| obnoxious |
extremely unpleasant or irritating. |
| oboe |
a slender double-reed woodwind instrument, consisting of a long, usu. wooden tube with finger holes or keys along it, which makes a penetrating, melancholy sound. |
| obscene |
offensive to accepted views of morality and decency, or to one's own sense of morality and decency. [3 definitions] |
| obscure |
weakly or poorly illuminated. [6 definitions] |
| observation |
the act or an instance of observing. [5 definitions] |
| observatory |
a building containing equipment for making astronomical or other kinds of scientific observations. |
| observe |
to perceive; see. [10 definitions] |
| observer |
someone who observes an event such as a meeting but does not participate in it. [2 definitions] |
| obsolete |
no longer in use, as a word or expression, or as a type of implement or equipment. [2 definitions] |
| obstacle |
that which impedes or prevents forward movement or progress; obstruction. |
| obstinate |
holding stubbornly to one's own ideas or purposes; unwilling to change. [2 definitions] |
| obstruct |
to clog or block. [3 definitions] |
| obstruction |
something that obstructs; obstacle or impediment. [3 definitions] |
| obtain |
to gain possession of; acquire. [2 definitions] |
| obtuse angle |
an angle greater than 90 degrees and less than 180 degrees. |