Keenly observant is a term used to describe someone who pays close attention to their surroundings and notices even the smallest details. The crossword solutions for this term are ORTHODOX (8 letters), Hawkeyed (8 letters) and Sharpeyed (9 letters). ORTHODOX means adhering to established or accepted standards, while Hawkeyed and Sharpeyed both refer to having sharp vision and being able to observe things with great accuracy.