Question

What is the definition of andesitic composition ?

Answer 1

Andesite: 
Is an extrusive igneous, volcanic rock, of intermediate composition, with anphanitic to porphyritic texture. In a general sence, it is the intermediate type between basalt and decite  and ranges from 57  to 63% silicon dioxide as illustrated inTAS diagrams.

Answer 2

Andesite can composition is a rock composed essentially of plagioclase feldspar and one or more mafic minerals, as hornblende or biotite.