catch on to

• graspSeize or understand
• understandGrasp the meaning
• realizeBecome aware of
• clickBrief sharp noise
• dawnDay's first glow

figure out · get it · comprehend · twig · see · light bulb · aha · wise up · clue in · pick up · discern · penetrate · fathom · latch onto · cotton to · tumble to · wake up · eureka