a full moon lacking perfect opposition to the sun during an eclipse
Syr
Kays 224:1↗ܐܢܕܝܢ ܩܠܝܠ ܠܒܪ ܡ݂ܢ ܩܛܪ̈ܬܐ ܡܬܟܝܢܝܢ ܢܗ݂ܝܪܐ܂ ܒܫܥܬܐ ܕܦܢܣܸܠܝܢܘ݁ܣ ܕܗܘ݂ ܦܓܘ݂ܡܝܐ ܕܣܗܪܐ܂ ܠܐ ܚ݁ܫܸܟ ܟ݁ܠܗˀndyn qlyl lbr m̱n qṭr̈tˀ mtkynyn nẖyrˀ. bšˁtˀ dpnselynwws dhw̱ pgw̱myˀ dshrˀ. lˀ ḥḥšek klhאנדין קליל לבר מן קטרתא מתכינין נהירא٠ בשעתא דפנסֶלינוֹס דהוּ פגוּמיא דסהרא٠ לא חּשֶך כּלהܐܢܕܝܢ ܩܠܝܠ ܠܒܪ ܡ݂ܢ ܩܛܪ̈ܬܐ ܡܬܟܝܢܝܢ ܢܗ݂ܝܪܐ܂ ܒܫܥܬܐ ܕܦܢܣܸܠܝܢܘ݁ܣ ܕܗܘ݂ ܦܓܘ݂ܡܝܐ ܕܣܗܪܐ܂ ܠܐ ܚ݁ܫܸܟ ܟ݁ܠܗˀndyn qlyl lbr m̱n qṭr̈tˀ mtkynyn nẖyrˀ. bšˁtˀ dpnselynwws dhw̱ pgw̱myˀ dshrˀ. lˀ ḥḥšek klhאנדין קליל לבר מן קטרתא מתכינין נהירא٠ בשעתא דפנסֶלינוֹס דהוּ פגוּמיא דסהרא٠ לא חּשֶך כּלהܐܢܕܝܢ ܩܠܝܠ ܠܒܪ ܡ݂ܢ ܩܛܪ̈ܬܐ ܡܬܟܝܢܝܢ ܢܗ݂ܝܪܐ܂ ܒܫܥܬܐ ܕܦܢܣܸܠܝܢܘ݁ܣ ܕܗܘ݂ ܦܓܘ݂ܡܝܐ ܕܣܗܪܐ܂ ܠܐ ܚ݁ܫܸܟ ܟ݁ܠܗܐܢܕܝܢ ܩܠܝܠ ܠܒܪ ܡ݂ܢ ܩܛܪ̈ܬܐ ܡܬܟܝܢܝܢ ܢܗ݂ܝܪܐ܂ ܒܫܥܬܐ ܕܦܢܣܸܠܝܢܘ݁ܣ ܕܗܘ݂ ܦܓܘ݂ܡܝܐ ܕܣܗܪܐ܂ ܠܐ ܚ݁ܫܸܟ ܟ݁ܠܗ: but if (during an eclipse) the luminaries are positioned a little outside of the nodes at the time of the full moon that is the p' of the moon, it does not go completely dark
"Waning" does not quite seem to fit the cited text. As stated clearly there, it refers to a full moon being slightly off of total opposition to the sun, resulting in a partial eclipse.