This word is used in Spain to name in a funny way all tourist from the north of Europe (French people sometimes are included too, but the majority are from England and Germany).
You can easily find a "guiri" because his/her skin is pale or extremely burned by the sun.
His/her hair is mainly blond or red.
When they are young, the usually spend all day and night drinking in the street or at the beach; and the like to shout a lot.
When they are adult, they wear sandals with socks (which we find very funny) and colorful shirts.
People sometines even are racist with them, because some of them walk naked in the streets and no one wants to see that.
But they leave here their money and we all know we need it.
Besides, our supermarkets are now full of foreign food and we have could try the peanut butter.
Disgusting, by the way.