1. To make something lighter. An example is taking inventory off a truck. 2. To liquidate a securities positions. Moving investment portfolio holdings to cash. Selling stocks or bonds to lighten up an investment portfolio is an example. 3. To tell another person to be less tense or to calm down. A colloquial term used casually. It might be said between two peers at work. A supervisor might informally say this to a subordinate . Familiarity between two people where one tells the other to lighten up is necessary because the term is casual in nature.
Black’s Law Online Dictionary
