What is a triangular pyramid called, if all faces are equilateral triangles?

Hint: In order to solve this problem we need to know that the triangular pyramid which has 4 triangular faces and if all the sides of the triangular pyramid is equal then it is called a triangular pyramid of equilateral triangles. Knowing this will solve your problem.

Complete step by step answer:
Triangular pyramid:
A triangular pyramid is a pyramid having a triangular base. The tetrahedron is a triangular pyramid having congruent equilateral triangles for each of its faces.
The figure of triangular pyramid also called tetrahedron can be drawn as,

Now if all the faces of the triangular pyramid are equilateral triangle then it will also be a triangular pyramid but all the sides are equal as well.
If the all sides of a triangular pyramid are equal implies that it is a tetrahedron. In case of a regular tetrahedron all the sides are equal. So, a regular tetrahedron is a solid with all the four triangular faces having equal sides.
Therefore, the triangular pyramid with all the faces of the equilateral triangle is called tetrahedron.

So, the answer is tetrahedron.

Note: Tetrahedron is a polyhedron or three-dimensional shape with at least three sides and polygonal base. A triangular pyramid is a pyramid with a triangle as a base and three triangular faces. It has four vertices or points and six edges. There are also rectangular, pentagonal, square, and hexagonal pyramids. All the triangles of tetrahedron are congruent and when all the sides of all the triangles are equal then it is a triangular pyramid with equilateral triangle and is called tetrahedron. Knowing this will solve your problem and will enhance your knowledge about triangular pyramids.