Engine SEIZING

Can anyone please explain what it means when the engine seizes?

thanks

Usually excessive heat or pressure/force has caused the lubrication between the parts to break down and metal to metal contact is made and, normally, metal to metal transfer is made and the parts effectively weld themselves together.

If the engine seized suddenly, especially if there was some sound at the same time, it may be due to a mechanical failure, breakage, of some sort.

Another common cause when the engine hasn't been used for a while is corrosion, as oxidised metals expand as part of the process and can lock parts together - with iron the rust's expansion is around 4 times the original volume of the iron, IIRC. This may be seen as pistons 'rusted'in place, or stuck valves that may be hit by pistons.

Do you have a specific case in mind?