The unofficial bastardized Latin motto of many organizations, particularly military units. "Semper", of course is the Latin word for "always". "Gumbi" refers to Gumby, a TV character made of clay. Thus, Semper Gumbi is translated as "Always Flexible."
G.I. Joe: "We were supposed to go back home a month ago but these Iraqis can't get their stuff together. Now we have to stay indefinitely."
G.I. Jack: "There's no use crying about it. Just suck it up and remember - Semper Gumbi."