Noun
A formal or elaborate argumentative discourse, oral or written; a disquisition; an essay; a discussion; as, Dissertations on the Prophecies.
Source: Webster's dictionaryA letter is now attached to the copy of King's dissertation held in the university library, noting that numerous passages were included without the appropriate quotations and citations of sources. Source: Internet
A dissertation in the AmE sense would be a thesis in BrE, though dissertation is also used. Source: Internet
After the United States declared war on Germany in 1917, Hubble rushed to complete his PhD dissertation so he could join the military. Source: Internet
Anton von Webern wrote his dissertation on the Choralis Constantinus of Heinrich Isaac and the contrapuntal techniques of his serial music may be informed by this study. Source: Internet
At Auburn, his research focused on theoretical atomic physics, and his dissertation — Discovery of Enhanced Recombination in Astrophysical Environments and the Implications for Plasma Diagnostics — focused on the study of planetary nebulae. Source: Internet
A dissertation in AmE refers to the final written product of a doctoral student to fulfil the requirement of that program. Source: Internet