The term 'on one's rocker' is an idiom that means someone is acting in a crazy or irrational manner. The crossword solutions for this term are SANE (4 letters) and SEATED (6 letters). This is ironic because the opposite of being on one's rocker is being SANE, and the opposite of being seated is being on one's feet. Therefore, these two words together can be interpreted as someone being seated and SANE, which is the opposite of being on one's rocker.