A nitrophyte is any plant that grows mainly at eutrophic places with a high nitrogen content in the soil. (The nitrogen in the air is not available for plants, it must be fixed in a compound.) A plant well known to be a nitrophyte is the stingnettle, among the cultivated plants maize.
Like with other ecological factors there is theoretically a distinction between a nitrophyte and a nitrophilous plant. This distinction makes sense with similar classifications (for examplexerophytes and xerophilous plants) but in this case the terms hardly make any difference since virtually no plant that is not nitrophilous has any reasons to prefer eutrophic soils.
Since nitrogen immissions in many soils increase due to industrial emissions and to fertilizing, nitrophytes are becoming more common whereas plants that cannot compete against them under eutrophic conditions lose ground. That is why hypotrophic ecosystems have such an important ecological value.