Synonyms for Field Mouse (same or very similar meaning)
WordNet sense 1 (any of various small mouselike rodents of the family Cricetidae (especially of genus Microtus) having a stout short-tailed body and inconspicuous ears and inhabiting fields or meadows):
voleWordNet sense 2 (any nocturnal Old World mouse of the genus Apodemus inhabiting woods and fields and gardens):
fieldmouseFrom the ODE community, based on WordNetadd/edit