1. small aquatic animals that are typically colonial and have a tubular body with tentacles around the mouth
Usage: biology; plural form

Examples

• The marine biologist studied the hydroids growing on the coral reef.
• Hydroids are often mistaken for small sea anemones by casual observers.
• The aquarium tank contained several species of colorful hydroids.
• These hydroids reproduce both sexually and asexually.
• The researcher collected hydroids from tide pools for laboratory analysis.
• Hydroids play an important role in marine ecosystems as filter feeders.