pistachio

pis‧ta‧chi‧o /pəˈstɑːʃiəʊ, pɪˈstɑːʃiəʊ $ pəˈstæʃioʊ/ BrE AmE noun (plural pistachios) [countable]
[Date: 1400-1500; Language: Italian; Origin: pistacchio, from Latin, from Greek pistakion, from pistake 'pistachio tree', from Persian pistah]
a small green nut:
pistachio ice cream

Oxford Advanced Learner's Dictionary

pistachio

pis·ta·chio [pistachio pistachios] [pɪˈstæʃiəʊ] [pɪˈstæʃioʊ] [pɪˈstɑːʃiəʊ] [pɪˈstɑːʃioʊ] noun
(pl. pis·ta·chios)

1. (also piˈstachio nut) countable the small green nut of an Asian tree

2. uncountable a pale green colour
Word Origin:

late Middle English pistace, from Old French, superseded in the 16th cent. by forms from Italian pistaccio, via Latin from Greek pistakion, from Old Persian.