Although in most online games, to gank means to kill a small group or individual by a much larger group, in Guild Wars ganking means to attack a target which is not capable of resisting an assault. The target can range anywhere from a Guild Lord, to flag runners to archer NPCs. The players performing the gank can range from a single character to all eight. Splitting your team into smaller segments for ganking purposes is common.
In Heroes' Ascent, the term gank is used to describe the tactic by which one or two teams gang up against another team to prevent them from winning. A team might gank if they realize that they cannot win, and instead of resigning, go after one team to prevent them from winning. They could also gank by immediately seeking to take another team out of the battle. They may whisper members of the third team and agree to team up. There are several reasons a team might gank but most commonly it is because they do not like the players or tactics of the team they chose to gank. Another reason may be to help friends, alliance or guild members on the third team win.
Back when "Victory or Death!" existed, a common last chance desperation strategy of many guilds was to attempt a Guild Lord gank close to "Victory or Death!" time. Any or all of the 8 GvG players rushed the backdoor of the map, or even ran through the enemy team (with ample snares) at a chance of possibly killing the Guild Lord. On maps with trebuchet or the Druid's Isle, for example, the gankers could body block door entrances or the vine bridge so that the enemy monks couldn't return back to heal their Guild Lord.