A narrow opening is a small space between two objects or surfaces. The crossword solutions for this term are SLOT (4 letters), CLEFT (5 letters), CRACK (5 letters), SLIT (4 letters), GAP (3 letters), CRANNY (6 letters), EYELET (6 letters), and FISSURE (7 letters). SLOT refers to a long, thin opening, while CLEFT is a split or CRACK in a surface. CRACK is a narrow break in a surface, and SLIT is a narrow cut or opening. GAP is a break or opening in a surface, and CRANNY is a small, narrow opening. EYELET is a small hole or opening, and FISSURE is a long, narrow opening or CRACK.