1992 Acura Legend indicates the antilock braking system is engaged

1992 Acura Legend mileage: 105,000. This has been going on for more than a year, and I do all my own mechanical work so I don't have a regular garage mechanic to ask about it. Often when I depress the brake pedal at 45 mph or faster it pushes back in the pulsating fashion that indicates the antilock braking system is engaged. The ABS warning light doesn't come on at any time. And there's no problem with the braking. But clearly, something's not right. What's up? Thanks, but I've been through difficulties with warped rotors before. That was more a shimmy and shake in the front end when I braked at high speed. In this case the brake pedal pushes back at me, pulsating, exactly/precisely the same as it does on ice or wet leaves when I put the ABS through its paces.