All dictionaries modify "walk," in defining "hike," with either strenuous or vigorous. And purists in the hiking set insist on taking that to mean rigorous, as in forced march.

But most of the organizations devoted to hiking in this area see no reason that those modifiers shouldn't be modified by "scenic," since trails offering magnificent vistas are abundant around Washington.

The oldest established social hiking clubs in the area are the Center and Capital clubs and the Wanderbirds, who operate all year. Capital and the Wanderbirds go by charter bus every week (usually Sunday) to trails in areas with magnificent vistas such as Shenandoah Park, the Blue Ridges and Massanuttens and Catoctins. The Wanderbirds always offer short (5-6 miles) choices as well as full-length treks (10-12 miles); Capital often does.

Center Club car-pools more often than buses, and occasionally has historic outings with expert guides -- in town, Gettysburg, Richmond, Philadelphia. Most of its dates are Saturdays. All three welcome nonmembers on most outings (for a slightly higher fee), and all have seasonal brochures listing scheduled outings. Call Capital at 829-2183; Center at 941-8743 or 891-2369; Wanderbirds at 256-5071 or 338-2920.

The grandad of hiking organizations is the Potomac Appalachian Trail Club, which evolved from pioneer outdoorsmen/ecologists who hewed out the network of trails, cabins, shelters and waterholes that gave it its name. It still maintains as its primary purpose maintenance and extension of "The Trail," and welcomes volunteers on projects most weekends. And the work is tempered with breaks and fellowship to enjoy the views. And getting there is half the fun. PATC also has "fun" hikes, at the moment under the direction of Chris Brunton. Call him at 560-8070. For general PATC information, call 638-5306.

There are two organizations in the area for serious trudgers who want to click off the miles with spartan company -- both members of the American Volkssport Association that stage "volksmarsches," which may give you a clue to their earnestness. They are the National Capital Area Federation of Volksmarschers, 703/680-4521, and the Air Force Data Services Center Volkssport Club, 695-6057.

Potomac Backpackers is a club that, as its name implies, tends to overnighters. Its emphasis is family, with less joie de vivre than the social clubs listed above. But most of the outings are scenic, and of course have the added advantage of sunsets, campfires and dawns. Call 598-4491.

Washington Women Outdoors is a limited-membership (obviously) organization that tends more to biking, camping, rafting etc., but has some hikes. Call 942-8677. And most of the jurisdictional recreation associations schedule hikes -- for example, Rockville Get Outdoors (424-8000, ext. 325) has an outing to Stony Man Mountain coming up with a mandatory pre-trip meeting Tuesday.

The Sierra Club has hikes of its own, with the emphasis on ecology rather than scenery, but the two are hard to separate. It maintains a DIAL-A-HIKE phone that lists its own and other treks: 547-2326. Similarly, the area chapter of American Youth Hostels, mostly biking, but some shank's mare -- 783-4943.

As in most fields, Washington is the place to live is you want to know everything there is to know about hiking, everywhere, because the headquarters of the American Hiking Association is here -- 234-4610.