1. Not woody, lacking lignified tissues. (wiktionary.org)
2. A plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground. Herbaceous plants may be annuals, biennials or perennials. (wikipedia.org)
3. Of, denoting, or relating to herbs (in the botanical sense). (Google Dictionary)
4. Refers to a plant that has a non-woody stem and which dies back at the end of the growing season. Characteristic of a non-woody herb or plant part.Pertaining to non-woody plants. (biology-online.org)
Word origin: From Latin herbaceus, from herba, from Old French erbe “grass, herb, plant” (12c.), from Latin herba “grass, an herb, herbage, turf.” Refashioned after Latin since 15c., but the h- was mute until 19c.