Related Clues:

• Transient
• Slippery
• Hard to grasp
• Hard to catch
• Hard to pin down
• Hard to find
• Evasive
• Hard to get
• Shifty
• Difficult to grasp
• Hard to nail down
• Difficult to understand
• Hard to pin down, slippery
• Evasive or intangible
• Slippery, hard to catch