ag ‧ glom ‧ er ‧ ate /əˈɡlɒmərət, əˈɡlɒmərɪt $ əˈɡlɑː-/ BrE AmE noun [singular, uncountable] technical
[ Date: 1600-1700 ; Language: Latin ; Origin: past participle of agglomerare 'to pile up' , from ad- 'to' + glomus 'ball' ]
a type of rock formed from pieces of material from a ↑ volcano that have melted together