"I did a stupid thing," Lee said in an interview that aired Sunday on "Oprah's Next Chapter" on OWN. "I don't know what my intention was."
Lee said he was angry over Trayvon Martin's death. "But angry does not -- it's not a justification for stupidity," Lee said.
Lee elaborated on the error by spelling it out: "There's nothing I can say that can defend what I did. Stupid. S-t-o-o-p-i-d."
Elaine and David McClain have sued Lee over fallout from the tweet and retweets. The couple had settled with Lee in March 2012, and the director of "Do the Right Thing" then tweeted an apology. The couple faced harassment and received hate mail after Lee's tweet.
In their suit, which made headlines last week, the McClains say they are fearful and that Lee encouraged "a dangerous mob mentality among his Twitter followers." The director had 240,000 followers last year when he delivered the erroneous tweet.
The McClains seek more than $15,000 and say their home's value has slid because of the Lee publicity.
About the earlier settlement, Lee told Winfrey: "We spoke. You've got to be a man. Say, 'I made a mistake' and learn from it."
Zimmerman was acquitted in Trayvon's fatal shooting.