You just made my point by describing x,y,z dimensions. How fast you're traveling within those known dimensions is called speed, no matter the angle or trajectory. If they want to call velocity by another term, fine, but most believe it to be the speed of a given object.
So, is the speed of light a velocity or just 186,000 miles per second as in speed? Yes, even light can be bent as in a prism or other within our perception and calculated physics. Maybe that's where they get the other 3 dimensions. This is all probably beyond my little brainpan.
Speed in a specified direction is velocity, as velocity always includes direction. In space, which is 3-dimensional, you have to say how fast you are moving in each of those 3 spatial dimensions. That is a 3-dimensional velocity (speed in x, speed in y, speed in z). The ‘speed’ in the direction of travel is the magnitude of the 3-dimensional vector (square root of the sum of the squares of the speed in each direction).
speed in x, speed in y, speed in z is a 3-dimensional velocity vector. You can compute the angle of travel from those values by trigonometry.
Light is another thing altogether and requires relativistic physics. It is just weird.