# pilidium

> English word · Noun

## Definitions
1. The free-swimming larva of certain proboscis worms, somewhat resembling a deerstalker hat. It has no resemblance to its parent, and the young worm undergoes development in its interior.

## Etymology
From Ancient Greek πῑλίδιον (pīlídion, “little cap”), diminutive of πῖλος (pîlos), probably influenced by other formations in -idium, like miracidium, planidium, and coracidium.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/pilidium