dendroidPronunciation: /ˈdɛndrɔɪd/Definition of dendroid adjective Biology (of a plant, marine invertebrate, or structure) tree-shaped; branching. noun Palaeontology a graptolite of a type that formed much-branched colonies, found chiefly in the Ordovician and Silurian periods. Order Dendroidea, class Graptolithina Origin: mid 19th century: from dendro- 'tree' + -oiddendroid in other Oxford dictionaries Definition of dendroid in the US English dictionary