Multimedia Inc., the South Carolina communications company, today acknowledged receiving a surprise $1 billion-dollar buyout bid from Lorimar but said the company is not for sale.

Lorimar, which produces movies and television programs and owns an advertising agency, offered $61 a share for Multimedia, whose management and founding families own 40 percent of the company's stock.

Earlier this week, Multimedia rejected another unsolicited offer of $60 a share that reportedly was made by former Treasury secretary William E. Simon through Wesray Corp., a New Jersey investment banking firm he controls.

The bidding for Multmedia started after an investor group including management and the founding families announced plans to take the company private in a leveraged buyout.

But after higher offers were made by outsiders, Multimedia announced earlier this week that its directors had replaced the leveraged buyout with a sweetened plan worth about $54 a share, or $900 million, that enabled stockholders to retain a reduced interest in the company

Multimedia is a Greenville, S.C., communications company that owns 43 newspapers, five television and 12 radio stations and 100 cable franchises. It also syndicates and produces television programs, including "The Phil Donahue Show." Multimedia, which earned $33.7 million, or $2.02 a share, on revenue of $304.4 million in 1984, is controlled by members of the Peace, Jolley, Furman and Sisk families.

Under terms of the most recent management buyout plan approved by directors, Multimedia shareholders can elect to give up part of the money offered for their stock and retain a share of their equity interest.

Multimedia also said that since South Carolina law requires holders of at least two-thirds of a company's shares to approve mergers, "no one should assume that any transaction will occur with" Lorimar or any other bidder.