Definition: atom x2 = floor(atom x1)
Description: Return the greatest integer less than or equal to x1. (Round down to an integer, towards -infinity.)
Comments: This function may be applied to an atom or sq_floor() to all elements of a sequence. The rules for sequence operations apply.

floor(a/b) is treated specially for performance reasons, as there is no point storing a floating point intermediate/parameter when the fractional part gets discarded immediately. There is a corresponding sq_floor_div() sequence operation to match that performance enhancement, which yields exactly the same results as sq_floor(sq_div()), only faster.
y = sq_floor({0.5, -1.6, 9.99, 100})
-- y is {0, -2, 9, 100}
Implementation: via :%opFloor in builtins\VM\pUnary.e (an autoinclude)
See Also: remainder, ceil, trunc