Allogamous is a term that refers to the fertilization of a plant with the pollen from another plant of the same species. It is the opposite of autogamous, which refers to plants that fertilize themselves. However, there are several other terms that can be used as synonyms for allogamous. For example, the terms outcrossing, cross-pollination, or xenogamy can be used to describe the process of allogamous fertilization. Additionally, words like heterogamous and cross-fertilizing can also be used to convey the same meaning. These terms are useful to describe plants that require external pollination to reproduce and are important for understanding plant biology and ecology.