Sync enter

From Guild Wars Wiki

A Sync enter, sync join, join spike, spike join, or team stacking occurs when two or more players attempt to join the same team of a "randomly" selected PvP arena (i.e. RA, AB, Dragon Arena, Rollerbeetle Racing) team. It is controversial because it sidesteps the nominal randomness of teams and can create highly skilled teams that are often difficult for non-join spike teams to defeat.

Sync enters, more often than not, take place in the International District where the player count is very low. Since fewer people are joining the type in that specific type of district (not the district number), you are more likely to enter at the same time as a friend and be on the same team.

Non-controversial syncs also occur. In PvE syncs are useful for certain missions, i.e. Vizunah Square and Unwaking Waters when teams on both sides wish to play with human counterparts. Players working on the Canthan cartography title often sync enter The Jade Quarry because there are typically not enough players to start a match.