The term DECLINE GRADUALLY can be broken down into four crossword solutions: EBB (3 letters), SLIDE (5 letters), WANE (4 letters), and TAPEROFF (8 letters). EBB is a verb meaning to recede or flow away, usually referring to the tide. SLIDE is a verb meaning to move smoothly and continuously in a particular direction. WANE is a verb meaning to gradually decrease in size, strength, or intensity. Finally, taperoff is a verb meaning to become gradually less in amount or intensity. All of these words describe the process of decline gradually, which is the overall term.