A French pastry-making term used to refer to a piece of rolled-out pastry. The pastry can be any pastry: pie pastry, pâte brisée, or puff pastry.
A piece of rolled-out pastry is “une abaisse de pâte.”
To roll out pastry is “abaisser la pâte.”
Sometimes, Abaisse can also be used to refer to a biscuit or sponge-cake layer.
Abaisser means literally “to lower”.
There are good alternative English terms — “rolled-out pastry”, or in the case of a sponge cake layer, either a “layer” or a “foundation”. More impressive, though, would be “underlying strata.”