I've never heard the word "rackless". You probably mean "reckless", which means "does something without thinking about the consequences." "Tom drives too fast and he never wears a seat belt. He's so reckless." A rack is some type of structure for holding things, almost like a shelf. "Put the salt back on the spice rack." It can also informally refer to a woman's breast. "She has a big rack."

Reckless means "without being careful". He was a reckless person who acted without thinking. Reck is not a word in the current language. It is very archaic.