In this book, you will learn the meanings of 1400 useful 12- to 14-letter words. You will also find the names of the parts of speech they belong to. I have also given synonyms for most of these words. "Letter Count" has been mentioned in the bracket after each and every word. Sample this:

01 -- abominableness [14] [n.] -- the state or quality of being extremely bad or unpleasant and causing a strong feeling of dislike or disapproval [synonyms: monstrousness, repulsiveness]
02 -- abstemiously [12] [adv.] -- in a sparing manner, avoiding too much in enjoyable activities such as eating food or drinking alcohol
03 -- abstractedly [12] [adv.] -- without paying attention to what is happening around you because you are thinking deeply about sth else; [synonyms: absentmindedly, inattentively, distractedly]
04 -- abstractionism [14] [n.] -- the principles that the mind obtains concepts by abstracting them from concepts it already has, or from experience.
05 -- abstractionist [14] [n.] -- a person who produces abstract works of art || [adj.] -- producing abstract works of art
06 -- acquisitively [13] [adv.] -- in a manner that shows eagerness to acquire and own money or new possessions (material things) in a greedy way [synonyms: graspingly, covetously, materialistically]
07 -- acrimoniously [13] [adv.] -- (of an argument, a speech, discussion, behavior, etc.) in an angry manner or in a bitter, sharp, harsh manner of language or tone
08 -- adaptability [12] [n.] -- (a). the quality of being able to adjust or be adjusted to deal with new and different situations or conditions [synonym: flexibility] | (b). the quality of being able to be modified or suited for a new use or purpose
09 -- adjectivally [12] [adv.] -- as, or in the manner or way of, an adjective
10 -- adulterously [12] [adv.] -- relating to a physical relationship (intercourse) between a married person and sb who is not their spouse or partner [synonyms: disloyally, treacherously]
11 -- advantageous [12] [adj.] -- good, useful, helpful or favorable in a particular situation [synonyms: beneficial, gainful]
12 -- advantageously [14] [adv.] -- in a manner that is good, useful, helpful or favorable in a particular situation [synonyms: beneficially, constructively, gainfully]
13 -- adventitious [12] [adj.] -- happening by chance or accident; not planned or designed
14 -- adventitiously [14] [adv.] -- in a manner that is happening by chance or accident; in a manner that is not planned or designed
15 -- aggrandizement [14] [n.] -- an increase in the power, wealth, importance or status of a person or country [synonyms: enhancement; extension]
16 -- alliteration [12] [n.] -- repetition of the initial letter or sound at the beginning of words in a sentence
17 -- amateurishly [12] [adv.] -- in a manner that is done incompetently, inexpertly or unskillfully [synonyms: incompetently, unprofessionally]
18 -- ambassadorial [13] [adj.] -- belonging to a high-ranking official, who is representative to a foreign country [synonym: diplomatic]
19 -- ambassadress [12] [n.] -- a high-ranking female official, who is representative to a foreign country; a female ambassador [synonyms: diplomat, envoy]
20 -- ambidextrous [12] [adj.] -- (a). able to use the right and left hands equally well | (b). (of a tool or instrument) designed to be used by right-handed and left-handed people with equal ease
21 -- ambidextrously [14] [adv.] -- meaning of the word
22 -- amphibiously [12] [adv.] -- (a). in a manner that is able to live/belong both on land and in water | (b). (of military operations) in a manner that involves soldiers landing or attacking at a place from the sea | (c). in a way that is suitable for use to operate on land or water; in a way that is able to operate on land or water
23 – antagonistic [12] [adj.] -- showing or feeling dislike or opposition [synonym: hostile]