The term 'be furtive' can be defined as to act in a sneaky or sly manner. This can be expressed by two five-letter crossword solutions: 'SNEAK' and 'SLINK'. To 'SNEAK' means to move quietly and stealthily, often with the intention of avoiding detection. To 'SLINK' is to move in a stealthy or sly manner, often with the intention of avoiding detection or confrontation. Both words imply a sense of secrecy and caution.