1. To awaken from sleep. I dreamt I was falling through a floor made of macaroni and cheese, when I suddenly woke up. I'm finding it harder and harder to wake up this early in the morning.

2. To cause someone to awaken from sleep. In this usage, a noun or pronoun can be used between "wake" and "up." I had to wake him up because his snoring had gotten so bad in the night. I have to have a cup of coffee in the morning to help wake me up. Go wake up your brother—we're leaving soon!

3. To become alert to or aware of something, especially something that needs to be recognized as a problem. The board of directors refuses to see the imminent danger facing the company. At this point, it will take a financial disaster to make them to wake up. You need to wake up to what's happening instead of ignoring the situation.

4. To cause someone to become alert to or aware of something, especially something that needs to be recognized as a problem. In this usage, a noun or pronoun is used between "wake" and "up." We're trying to wake people up to the horrible reality of global meat production. If investors were feeling complacent before, this earnings report ought to wake them up.