ثن: الثُّنَّةُ: شَعَرَاتٌ مُشْرِفَاتٌ على رُسْغِ الدّابَّةِ من خَلْفٍ. وما ذُوْنَ السُّرَّةِ من أسْفَلِ البَطْنِ فَوْقَ العانَةِ، وجَمْعُها ثُنَنٌ.وكُنَّا في ثُنَّةٍ من الكَلإِ وغُنَّةٍ: أي في كَلإٍ كَثِيرٍ.والثِّنُّ: البالي من الحَشِيْشِ العَفِنُ. وإذا تَكَسَّرَ يَبِيْسُ النَّبْتِ فهو الحُطَامُ، فإذا رَكِبَ بَعْضُه بَعْضاً فهو الثِّنُّ.وأثَنَّ الهَرْمُ: بَلِيَ؛ إثْنَاناً.وما اسْوَدَّ من كُلِّ العِيْدَانِ: ثِنٌّ.

ثن2 ثنّن He (a horse) lifted his ثُنَّة [or fetlock] so that it did not touch the ground in his running, by reason of his briskness, or lightness: (M:) [or] his ثُنَّة touched the ground in consequence of his being ridden by a heavy person. (T.) 4 اثنّ He (a weak old man) became wasted and worn out. (K.) 5 تثنّن He pastured, or fed, upon ثِنّ [q. v.]. (T.) ثِنٌّ Dry herbage: (S:) or dry herbage when it lies heaped together, one part upon another: (T:) or dry herbage, (K,) or what has become dried up of حَلِىّ and بُهْمَى and حَمْض, (M,) when it is much in quantity, and lies heaped together, one part upon another: or what has become black of any branches, or twigs; not consisting of بَقْل nor of عُشْب: (M, K:) or dry herbage broken in pieces: (IDrd, M:) or [simply] herbage, or pasture: (Th, M:) or herbage that is weak, and soft, or easily broken. (IJ.) ثُنَّةٌ, of a human being, (Lth, T,) The part below the navel, (Lth, T, M,) above, (Lth, T,) or extending to, (M,) the hair of the pubes, (Lth, T, M,) in the lower part of the belly; (Lth, T;) the part between the navel and the hair of the pubes: (S:) or the thin skin (مُرَيْطَآء) between the navel and the hair of the pubes: (M, K:) or the hair of the pubes, (T, M, K,) itself. (M.) b2: And, of a horse (T, S, M, K) and the like, (T, S, K,) The fetlock; i. e. the hairs on the hinder part of the pastern-joint, (T, S, M, K,) hanging down (S, M) over the part called أُمُّ القِرْدَان so as nearly to reach the ground: (S:) pl. ثُنَنٌ. (S, M.) b3: كُنَّا فِى ثُنَّةٍ مِنَ الكَلَامِ وَغُنَّةٍ (tropical:) [app. meaning We were engaged in light and confused talk] is a metaphorical saying, borrowed from the ثُنَّة of the horse and the singing [or humming or buzzing of the flies and other insects] of the meadow or garden. (A, TA.) ثِنَانٌ Numerous, or abundant, and tangled, or luxuriant, plants or herbage. (T, K.)