Main Entry: immigrant : one that immigrates : as a : a person who comes to a country to take up permanent residence b : a plant or animal that becomes established in an area where it was previously unknown.
Main Entry: emigrant 1 : one who emigrates (to leave one's place of residence or country to live elsewhere) 2 : a migrant plant or animal.
in addition, i think that immigrant usually is referred to 移民 while eimgrant can be referred to 農民工.