/ ˌsʌrəpˈtɪʃəs; NAmE ˌsɜːr-/ adjective
done secretly or quickly, in the hope that other people will not notice
SYN furtive :
She sneaked a surreptitious glance at her watch.
► sur·rep·ti·tious·ly adverb
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WORD ORIGIN
late Middle English (in the sense obtained by suppression of the truth ): from Latin surreptitius (from the verb surripere , from sub- secretly + rapere seize) + -ous .