The "New Right" - that ethereal catchword that political pundits use offhandedly to describe what they perceive as an ideological movement - is easier to label than it is to define.

To some Old Guard conservatives, the New Right means little more than a network of Washington-based political organizations that use direct-mail fundraising and aggressive lobbying techniques to support conservatives.

Richard A. Viguerie, the phenomenally successful direct-mail fundraiser whose Falls Church, Va., firm has amassed lists with names of 5 million right-of-center contributors, is at the core of the network, the old conservatives maintain. The component parts, they say, are Viguerie's clients.

Leaders in the neo-conservative movement, however, offer a broader definition.

"It's a new dimension of conservative activity . . . an explosion of new, aggressive and effective conservative organizations that have put aside their difference and jealousies and are working together for a broader constituency," said Rep. Philip M. Crane (R-Ill.), chairman of the American Conservative Union (ACU).

That constituency, the network of conservative leaders has decided, includes a "conservative majority" of blue-collar workers and "ordinary" people who are frustrated over rising taxes and the largess of costly federal social programs.

Most of the leaders came out of the Young Americans for Freedom movement of the 1960s, and while the elements of the network have had their differences in the past, they have begun to settle them in regular meetings on Capitol Hill.

Crane said he holds monthly luncheon "ecumenical meetings" at the Capitol Hill Club where the neo-conservatives map out common strategy and discuss their differences. Usually on Friday mornings they meet at the Committee for the Survival of a Free Congress.

Crane said the "best culmination" of the strategy sessions came in the four-city "truth squad" blitz earlier this month when a coalition of conservative senators and congressmen hopscotched the country aboard a chartered jetliner to voice their opposition to the Panama Canal treaties.

"That was a drill, a realization we can work co-operatively and get out to reach the people," said Crane. He added that more such trips will be held on other key social and political issues.