Some long words that start with the letter "l" include labefactation, lachrymogenic, largiloquent, lautenclavicymbel and lendumbrilate. A few more common long "l" words are libertarianism, liquification, logocentrism, lugubrious and luminescence.
Labefactation consists of 13 letters and means a weakening decay or an overthrow. An example of labefactation used in a sentence comes from a literary disagreement regarding Gulliver's Travels: "There is in it such a labefactation of all principles as may be injurious to morality."
Lachrymogenic is also a 13-letter word and serves to indicate things that cause tears or weeping to occur. This word falls in a family that stems from the word "lacrima," which itself is a dialect-altered form of the Greek word for tears, "dakryma." Other words in the same family include lachrymator, lachrymiform, lachrymal, lachrymation and lachrymal.
Largiloquent contains 12 letters and comes from the Latin word "largiloquus." To be largiloquent is to be talkative or full of words. A largiloquent person is one who speaks typically in a bombastic or boasting manner.
Lautenclavicymbel is a word with 17 letters and represents a lute harpsichord made with strings of guts. Lendumbrilate is a 13-letter verb for the action of believing gullibly in the veracity of a word.