Approaching furtively means to move in a stealthy manner, often with the intention of avoiding detection. The crossword solutions for this term are 'SIDLE, ' 'SNEAK, ' and 'stealup.' To SIDLE is to move sideways or obliquely, often in a sly or cautious manner. To SNEAK is to move quietly and carefully, usually in order to avoid being noticed. To stealup is to move stealthily, often with the intention of avoiding detection.