Both Uses

treason
in
The Man Without a Country
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Only, when the grand catastrophe came, and Jefferson and the House of Virginia of that day undertook to break on the wheel all the possible Clarences of the then House of York, by the great treason trial at Richmond, some of the lesser fry in that distant Mississippi Valley, which was farther from us than Puget's Sound is to-day, introduced the like novelty on their provincial stage; and, to while away the monotony of the summer at Fort Adams, got up, for spectacles, a string of court-martials on the officers there.†
Chpt Rest

treason = an act of betrayal
Danger or no danger, delicacy or no delicacy, who was I, that I should have been acting the tyrant all this time over this dear, sainted old man, who had years ago expiated, in his whole manhood's life, the madness of a boys treason?†
Chpt Rest *

Definitions:

(1) (treason)
betraying someone or something -- typically betraying one's own country

(in this context, to betray is to not be loyal--often by helping enemies)
(2) (meaning too rare to warrant focus)