Preloading is when a player battles a team, gets beaten but “submits” the battle, meaning the next player who attacks that team will find them with full turn meter.
Most guilds would want members to only submit their attempt if they at least defeat one character.
mgkkain HotBot has a command that will check this for you - / twgamezonelog. Not sure when it was first available, but we found it very useful. We had a handful of members who didn’t realise preloading was a bad thing but they soon stopped doing it. Apart from one person who TM loaded virtually every TW, before he became another guild’s problem.