swamp (swɒmp ) Word forms: plural , 3rd person singular present tense swamps , present participle swamping , past tense , past participle swamped. 1. variable noun. A swamp is an area of very wet land with wild plants growing in it. Synonyms: bog, marsh, quagmire, moss [Scottish , Northern England , dialect] More Synonyms of swamp. 2. verb. If something swamps a place or object, it fills it with water.