A timeskip is a storytelling device often used in manga, where the author will suddenly skip ahead a significant amount in the plot of a story, usually at least several years. This is often done after an important conflict is resolved in order to set up the next part of the story.
When making vs. threads, posters often specify "Pre" or "Post" timeskip versions of characters, as characters tend to change in power over these breaks.
Examples of series with timeskips:
- Naruto (skips two years)
- 666 Satan (skips a few years)
- Bastard!! (has 2 skips, each several years)
- Claymore (had a 7 year timeskip after the battle of Pieta)
- Dragon Ball (does this very often, usually skipping several years between arcs)
- Jojo's Bizarre Adventure (the transition from each part to the next could be considered a timeskip, though part 7 takes place in a different universe than part 6)
- Love Hina (timeskip of several years at the end)
- Magical Girl Lyrical Nanoha (the various series take place several years apart from each other, most notably Nanoha grows quite a bit between A's and StrikerS)
- One Piece (skips 2 years)
- Tengan Toppa Gurren-Lagann (there is a skip of a few years between the first and second parts of the anime)
- Yu-Gi-Oh! (each new series occurs after a timeskip)
Note: Has nothing to do with time manipulation.