The short answer:
It stands for "English"
The long answer:
The definitions are derived from Wiktionary, but rather than showing the whole Wiktionary page, I want to show just the meaning(s) of each word. Fortunately, the Wikimedia Foundation generously provides a tool for retrieving the underlying data for any entry. That data is provided in a coded form. So when you click on the word agin, a call goes out to the Wiktionary website, which provides the following data:
<?xml version="1.0"?><api batchcomplete=""><warnings><main xml:space="preserve">Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes. Use [[Special:ApiFeatureUsage]] to see usage of deprecated features by your application.</main><revisions xml:space="preserve">Because "rvslots" was not specified, a legacy format has been used for the output. This format is deprecated, and in the future the new format will always be used.</revisions></warnings><query><pages><page _idx="927863" pageid="927863" ns="0" title="agin"><revisions><rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">{{also|Agin}}
==English==
===Etymology===
From {{der|en|sco|agin}}, variant form of {{m|sco|again||against}}.
===Pronunciation===
* {{IPA|en|/ə.ˈɡɪn/}}
* {{rhymes|en|ɪn}}
* {{hyphenation|en|a|gin}}
===Adverb===
{{en-adv|-}}
# {{lb|en|colloquial|or|now|_|often|humorous}} {{alternative form of|en|again}}
#* '''1859''', {{w|Charles Dickens}}, "A Tale of Two Cities", in ''{{w|All the Year Round}}'', vol. 1, p. [http://books.google.com/books?id=1NIRAAAAYAAJ&output=html&q=agin&pg=PA98 98]:
#** ''At which juncture, he exclaimed, in a voice of dire exasperation : “Bust me, if she ain't at it '''agin''' !”''
{{anchor|en-prep}}
===Preposition===
{{en-prep}}
# {{lb|en|colloquial|or|now|_|often|humorous}} {{alternative form of|en|against}}
#* '''1859''', ''{{w|Harper's New Monthly Magazine}}'', vol. 19, p. [http://books.google.com/books?id=IEhGAAAAcAAJ&output=html&q=agin&pg=PA278 278]:
#*: [The Court] said: "Young man, this ere Court is satisfied that there ain't nothin' in the laws of Vermont '''agin''' tippin' over a churn full of sap. {{...}} But I want ye should remember one thing—that this ere Court has made up his mind that it's a very naughty trick, and it's a shame that there's so many maple-trees in the State, and no law '''agin''' tippin' over sap."
#* {{quote-book|en|title=[[w:The Adventures of Tom Sawyer|The Adventures of Tom Sawyer]]|page=228|author=[[w:Mark Twain|Mark Twain]]|year=1876|passage=when I got to that old shackly brick store by the Temperance Tavern, I backed up '''agin''' the wall to have another think.}}
===Anagrams===
* {{anagrams|en|a=agin|Agni|Angi|Gain|Gina|NGIA|Nagi|Ngai|a- -ing|gain|gain-|gina|inga}}
----
==Scots==
===Preposition===
{{head|sco|preposition}}
# {{alternative form of|sco|again}}</rev></revisions></page></pages></query></api>
It's then up to the Chihuahua software to extract the relevant portions and format them for display in the little definition box. Unfortunately the coding system used by Wikipedia and Wiktionary is quite complex, and not necessarily fully documented. So occasionally something is presented in a weird fashion. As in the two examples you show, yelnats.
From the definition panel, you can always get the definition as presented by Wiktionary. Just click on the Wiktionary link at the bottom of the panel.