glow·worm | \ˈglō-ˌwərm \

Definition of glowworm 

: any of various luminous insect larvae or adults with wings rudimentary or lacking especially : a larva or wingless female of a firefly (family Lampyridae) that emits light from the abdomen

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This is any crawling, luminous insect that emits light either continuously, or in prolonged glows, rather than in the brief flashes that are characteristic of most fireflies. Glowworms include larvae and adult (often wingless) females of fireflies and certain other beetle species, as well as the larvae of certain gnat species. They are widely distributed. There is great diversity in the size, number, location, and structure of the bioluminescent organs of glowworms.

Examples of glowworm in a Sentence

Recent Examples on the Web

The prey is drawn in by the glowworm's bioluminescent abilities, similar to a porch light that attracts insects. Liz Langley, National Geographic, "How Fireflies Glow (and What Really Turns Them On)," 2 July 2016

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'glowworm.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of glowworm

14th century, in the meaning defined above

History and Etymology for glowworm

Middle English

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Dictionary Entries near glowworm


glow switch

glow tube





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The first known use of glowworm was in the 14th century

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English Language Learners Definition of glowworm

: a type of insect that produces a small amount of light from its body


glow·worm | \ˈglō-ˌwərm \

Kids Definition of glowworm

: an insect or insect larva that gives off light

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lying above or upon

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