The term 'stick in the mud' is an idiom used to describe someone who is unadventurous, dull, and resistant to change. The crossword solutions for this term include MIRE (4 letters), BEMIRE (6 letters), EMBED (5 letters), FOGY (4 letters), REED (4 letters), STODGY (6 letters), KILLJOY (7 letters), OLDFOGEY (8 letters), WETNOODLE (9 letters), WETBLANKET (10 letters), and COFFEESTIRRER (13 letters). All of these words are related to the idea of being stuck in one place or state, and not wanting to move forward or try something new.