A plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests WordNet 3.0 & Open English WordNet

In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Wikipedia

Herbaceous plants are vascular plants that have no persistent woody stems above ground. Wikipedia

A plant that lacks a woody stem Wikipedia Disambiguation

Plant part used for flavoring, food, medicine, or perfume Wikidata

Plant which has no persistent woody stem above ground Wikidata

Any green, leafy plant, or parts thereof, used to flavour or season food. OmegaWiki

A plant whose stem is not woody and does not persist beyond each growing season. Wiktionary