impost.

1. A block or projecting member from which an arch begins to rise.

2. A tax or duty imposed by an authority.

Use it for

Words that belong together

• arch impost
• impost block

On the page

A carved impost marked the start of the arch.

Rain had worn the impost above the doorway smooth.

Usage notes

Primary category: architecture. Forms: Singular impost; plural imposts. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings.