Basically, despite stiff competition, "krautrock" might just be the single most bullshit genre term of all. The groups tagged with it hated it and because the wide range of sounds considered to be krautrock (everything from motorik grooves to electronic ambiance to bluesy hard rock to something which resembles US psych and/or UK prog) it doesn't really give the perspective listener an idea of the musical style, which is the whole point of a genre name in the first place.
Yes, I'm a huge krautrock fan and am a sucker for a lot of stuff under that particular umbrella but as a description it's fairly useless. If I had to describe it, I'd simply call it psychedelic European (mostly German) music. I truly think that in a sense, a lot of krautrock was basically a continuation of 60's psych and that in the 70's, the 60's psych influence sorta splintered into the earthy and spiritual side with krautrock whereas the more intellectual and escapist tendencies tended to manifest themselves more in prog 9though again, a few krautrock groups basically did their own version of prog).
One last word about genres- they often come down to arrangement rather than composition and while Gentle Giant are clearly too complex (not to mention white and nerdy) to be considered funk, if you're talking pop songs, it's pretty easy to them whatever genre you want purely by how you arrange them. Zappa used to do this all the time- had hand signals for different genres, pretending to twist a dreadlock meant "play reggae" ie play bar chords in a steady rhythm while emphasizing the upstroke. Genres are often superficial and can simply be thought of as whatever clothes the composer has chosen to dress their composition in.