Transactional lobbying, noun. 1. Providing a campaign contribution to a lawmaker in exchange for a political favor. 2. The exchange of check-containing envelopes between lobbyists and politicians linked to Congressional earmarks. see also: quid pro quo, bribery.

You may have seen the much-talked-about article in the New York Times about Brent Wilkes, the defense contractor who (along with Mitchell Wade) has been named in the bribery scandal that forced the resignation and plea deal of former Representative Duke Cunningham.  If you haven't, check it out - it's a disturbingly open account of how business is accomplished these days in Congress.