Tête-bêche is a French expression which describes the position of two people lying, one's feet facing the other's head. It's a corruption of bêchevet, which means "double bedhead" (a bed with bedhead at each end).

Looks like it's a philatelic term. It would be pronounced like "tet besh".

In philately, tête-bêche (French for "head-to-tail", lit. "head-to-head") is a joined pair of stamps in which one is upside-down in relation to the other, produced intentionally or accidentally. Like any pair of stamps, a pair of tête-bêches can be a vertical or a horizontal pair.

“Anti-counterfeiting device on paper money which consists of a design that appears twice, each occurrence being upside-down relative to each other. Its purpose is to make counterfeiting of that note more detectable, even to the average citizen not well-versed in determining the authenticity of paper money.”

An example is shown of the Brazilian 100 cruzeiros note, Pick 198. Literally, the term means “head-spade.”

The Stacks-Bowers cataloguer is using the term to apply to a pair of notes, one note printed upside-down relative to the other, rather than to the design of a single note.

With the diacriticals added, the term is tête-bêche.