Denshi Jisho — Online Japanese dictionary

Found 2 words.

外界 がいかい physical world; the externals
Common word, Noun, No-adjective 
外海 がいかい ocean; open sea
Noun 

You can also

Try a Yahoo Jisho search for がいかい .
Try a Goo Jisho search for がいかい .
Try a Google search for がいかい .