The concept of "hot" and "cold" slots refers to machines that seem to pay out frequently or not at all

https://www.tumblr.com/noisyoutlawnomad/785953177123110912/checking-out-distinct-perk-rounds-in-popular-port

The suggestion of "sizzling" and "bloodless" slots refers to machines that seem to pay out probably or on no account, although those traits are not directly random.