It has two meanings:
1. An Anglophone (or native English speaker) who speaks French as a second language that is:
a) too lazy to think of the correct translation for what they're saying, and therefore incorporate English words into their sentences, or
b) make a direct word-for-word translation of what they wish to say, in which case the translated term doesn't make sense in French.
A common thing done by French Immersion students, especially in Canada.
2. English words that are also used in French.
Franglais speaker: "Je ne care pas." ("I don't care.")
b) Franglais speaker: "Yo, longtemps, pas voir!" (Word-for-word translation of "Yo, long time, no see!")
French speaker: "Quoi...?"
2. "Le soccer," "le hot dog" and "le ski" are examples of English words that are used in the French language.