diabase

UK: /ˈdaɪəˌbeɪs/ US: (dī′ə bās′)

WordReference Random House Unabridged Dictionary of American English © 2026

di•a•base  (dī′ə bās′), n. [Petrol.]

1. Rocks a fine-grained gabbro occurring as minor intrusions.
2. Rocks [Brit.] a dark igneous rock consisting essentially of augite and feldspar;
   an altered dolerite.

• French, equivalent. to dia- (error for di- two) + base base¹
• 1810–20

di′a•ba′sic, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

diabase / ˈdaɪəˌbeɪs/ noun

1. an altered dolerite
2. 
   another name for dolerite

Etymology: 19th Century: from French, from Greek diabasis a crossing over, from diabainein to cross over, from dia- + bainein to go

ˌdiaˈbasic adjective