While you freestyle, have the DJ or another MC periodically cut the beat (mute the beat track) while you continue to rap a cappella until the beat comes back.
Keep your time and rhythm with the original beat, so you’re still on time when it comes back. When the beat cuts out, all the audience hears is you, so make it sound tight, punchy, and memorable. If you’re working on some narrative story or other idea, it might be best to drop what you were saying and insert some amazing hype line. When the beat cuts out, a lot of people will mumble something or just trail off. If you’re going to win people over — if they are going to remember one line you said all night — this will be it.
This is a very important skill if you’re freestyling over a DJ at a house party or club. At a party, most of the people listening won’t be able to really hear what you’re saying anyway, but they will when the DJ cuts the beat. Practice visually communicating with the DJ with a look or a nod to create setups like this. Ideally, everything you say is amazing enough to stand alone. If you know the music you can predict when this might happen. In real situations, anything can happen, so be ready for this move anytime. Be flexible with your flow.