From <span class="searchmatch">spiffing</span> + -ly. <span class="searchmatch">spiffingly</span> (comparative more <span class="searchmatch">spiffingly</span>, superlative most <span class="searchmatch">spiffingly</span>) (UK, colloquial) In a <span class="searchmatch">spiffing</span> manner; wonderfully, marvellously...
often used in imitation of upper-class speakers. spiffy spliffy <span class="searchmatch">spiffingly</span> <span class="searchmatch">spiffing</span> present participle and gerund of spiff Oxford English Dictionary...