https://en.wiktionary.org/wiki/ノシ
https://en.wikipedia.org/wiki/Shift_JIS_art
https://ja.wikipedia.org/wiki/アスキーアート
「ASCII art」とは本来、英語コミュニティにおいて「ASCII文字コードに含まれる文字・記号を用いた表現」のことを指した。日本語の入力環境としてはASCIIコードよりもシフトJISやEUC-JPなどが主流だが、テキストアート一般を指す語として日本語でも「アスキーアート」と呼んでいる。

I don't think [int] is correct. As the jitenon entry says, it's a symbol. のし is just a reading for the symbol.
This wouldn't typically be described as "ASCII art" in English as ノ and シ aren't ASCII characters. The term is used more loosely in Japanese.

@@ -8 +8 @@
-<pos>&int;</pos>
+<pos>&unc;</pos>
@@ -10 +10 @@
-<s_inf>from ASCII art using ノ and シ to represent a waving hand</s_inf>
+<s_inf>from text-based emoticons using ノシ to represent a waving arm</s_inf>
@@ -12 +12 @@
-<gloss>goodbye</gloss>
+<gloss>see you later</gloss>

Seems it's written as a term now. Trimming the nose.

@@ -10 +10 @@
-<s_inf>from ASCII art which uses the characters ノ and シ together to represent a waving hand</s_inf>
+<s_inf>from ASCII art using ノ and シ to represent a waving hand</s_inf>

The jitenon kokugo entry that I linked mentions that it is sometimes read as のし.
>> 読み方は単なる記号のため「無し」とされる場合と「のし」とされる場合がある。

This was previously added in 2007 and deleted in 2014 (entry 2210500). Rene commented "it's not a 'word', so it doesn't belong in a dictionary any more than ascii art".