A pose ball is an object in Second Life that poses or animates a user's avatar on screen when touched or sat on.
Pose balls used to be everywhere in the early stages of Second Life. However, in recent years, their use and appearances have declined in a strive for realism. Pose balls doesn't have to be literal spheres; any object can be made into a poseball - so rather than sitting on a chair by clicking a ball floating above the chair, you might simply click the chair itself. However the sphere is still widely used in new creations and old alike, as a symbolic cue to express oneself.
Some of the more popular pose balls tend to be ones that pose and animate romantic or sexual situations between characters (for which two or more pose balls are placed beside each other, often coloured pink and blue for female and male), although there are many examples of non sexual poses. Advanced poseballs may offer multiple animations through a menu or keyboard input, adding some varity.