Quadrate Cross

or Square Cross

A cross with four equal length arms is referred to as a 'Quadrate' or 'Square' Cross

As a Christian cross, the Quadrate Cross reminds us of the four Evangelists going out to the four corners of the earth. 

Four is a number often associated with the natural earth: the four seasons, and north, south, east & west. Similarly with the spiritual earth, God's name in Hebrew has four letters and to the Greeks, four represented order and stability as opposed to chaos.

Quadrate means 'square'. An extension of this meaning is to align, correspond, agree, suit. "To square things up" means to put matters in order. Another name for this cross is Square Cross, but in fact any cross with equal-length arms is considered a Square Cross. (See for example, the Greek Cross.)

In a coat-of-arms, to fit the shape of an escutcheon (shield) a cross is often shortened so that the length is the same as the width.

See the St. Chad's Cross and also image index for other examples.