A tripoint, or trijunction (also, if inexactly, known as tri-border area), is a geographical

Geography

Geography is the science that studies the lands, features, inhabitants, and phenomena of Earth. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...

 point at which the border

Border

Borders define geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states and other subnational entities. Some borders—such as a state's internal administrative borders, or inter-state borders within the Schengen Area—are open and...

s of three countries

Country

A country is a region legally identified as a distinct entity in political geography. A country may be an independent sovereign state or one that is occupied by another state, as a non-sovereign or formerly sovereign political division, or a geographic region associated with a previously...

 or subnational entities meet.

There are currently 157 international tripoints (i.e., tricountry points) by some accounts, and as many as 176 (or even 207) by others, but in any case these counts include a few condominial and buffered trijunctions that are technically tri lines or tri areas rather than simply tripoints.