If something is counterintuitive it means it's the opposite of "intuitive" — in other words it's not easily understood in an instinctive, unconscious way. A red light for "go" and a green light for "stop" would be highly counterintuitive, for example.

A classic example of the intuitive/counterintuitive divide can be found in computers: today they're so easy to use a toddler can handle them; early ones were so counterintuitive they remained a head-scratching mystery to all but a few techies. Writing tip: note that counterintuitive is one of those words that used to be commonly hyphenated (like "nonetheless" and "secondhand") but is now generally spelled as a single word.

Definitions of counterintuitive

adj contrary to what common sense would suggest

not reasonable; not showing good judgment