rhopaloid adjective 1noun 1forms 3 adjective1 •Having a shaft or tentacle with an uneven diameter.Moreover, septa of Amplexocarinia are not rhopaloid , nor are they long in early stages comparable to early stages of Bradyphyllum . — 1961 noun1 •A rhopaloid shaft or tentacle.The principal tentacular nematocysts are homotrichous microbasic rhopaloids, the capsule averaging 25–26μ long by 15–18μ across. — 1967 formsrhopaloids · more rhopaloid · most rhopaloid