лиляк

• IPA^(key): [ˈlilʲɐk]

Borrowed from Ottoman Turkish لیلاق, superseded in Modern Bulgarian by люляк (ljuljak).

ли́ляк • (líljak) m

1. (dialectal, dated) Alternative form of лю́ляк (ljúljak)

• лилав (lilav, “purple”)

• “лиляк”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Sofia: Bulgarian Academy of Sciences, 2014
• Georgiev, Vladimir I., editor (1986), “лиляк¹”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volumes 3 (крес¹ – мѝнго¹), Sofia: Bulgarian Academy of Sciences Pubg. House, page 403

Кожна мембрана (лил) формираща крилото на лиляците

Probably from лил (lil, “membrane”) +‎ -як (-jak) with a similar semantic basis as dialectal Russian кожа́н (kožán, “bat”) (from Russian ко́жа (kóža, “skin”)). Cognate with Macedonian лилјак (liljak, “bat”), Ukrainian ли́ли́к (lýlýk, “bat”), and loaned into Romanian liliac (“bat”).

ли́ляк • (líljak) m (diminutive ли́ляче)

1. (dialectal) bat (flying mammel of order Chiroptera)

   Synonyms: (colloquial) сля́по пи́ле (sljápo píle), при́леп (prílep)

• ли́лек m (lílek), лилека́на f (lilekána)

• лил (lil, “skin, membrane”) (dialectal)
• лист (list, “sheet”)

• “лиляк²”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Sofia: Bulgarian Academy of Sciences, 2014
• Georgiev, Vladimir I., editor (1986), “лиляк²”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volumes 3 (крес¹ – мѝнго¹), Sofia: Bulgarian Academy of Sciences Pubg. House, page 403
• Nayden Gerov (1899) “ли́лякъ”, in Рѣчникъ на Блъгарскꙑй язꙑкъ. Съ тлъкувание рѣчи-тꙑ на Блъгарскꙑ и на Русскꙑ. [Dictionary of the Bulgarian language]‎ (in Bulgarian), volume 3, Plovdiv: Дружествена печꙗтница "Съгласие.", page 13