<span class="searchmatch">fidēiusserās</span> second-person singular pluperfect active indicative of fidēiubeō...
fidēiussimus fidēiussistis fidēiussērunt, fidēiussēre pluperfect fidēiusseram <span class="searchmatch">fidēiusserās</span> fidēiusserat fidēiusserāmus fidēiusserātis fidēiusserant future perfect...