cited

Floor

float floor(float x)  
vec2 floor(vec2 x)  
vec3 floor(vec3 x)  
vec4 floor(vec4 x)

The floor function returns the largest integer number that is smaller or equal to x. The input parameter can be a floating scalar or a float vector. In case of a float vector the operation is done component-wise.

Side note: The return value is of type floating scalar or float vector although the result of the operation is an integer.