It's a string of letters that convey a meaning, so yes, it's a word. It also has the blessing of being listed in most dictionaries. Both forms, ironic and iron

It's a string of letters that convey a meaning, so yes, it's a word. It also has the blessing of being listed in most dictionaries. Both forms, ironic and ironical are valid and in casual settings tend to be used interchangeably. In a more formal sense, one would say a work that uses irony can be describe as ironical, whereas the events themselves are ironic.