isogram

plural isograms

1. A word in which no letter of the alphabet occurs more than once.

   For convenience, we can refer to an isogram of order n as an n-isogram. The examples in (2a) are 1-isograms, (2b) 2-isograms, and (2c) 3-isograms. Second- and third-order isograms are also sometimes referred to as pair and trio isograms respectively, but I will not use these terms here.

   2017 January 1, Florian Breit, “The Distribution of English Isograms in Google Ngrams and the British National Corpus”, in Bangor University, page 2

2. A line on a map or chart, such as a contour line, joining points that have the same value for some quantity.

   Synonyms: isoline, isopleth, isarithm