From Longman Dictionary of Contemporary Englishpenknifepen‧knife /ˈpen-naɪf/ noun (plural penknives /-naɪvz/) [countable] DTZa small knife with blades that fold into the handle, usually carried in your pocket SYN jackknife
Examples from the Corpus
penknife• He laid the telephone and torch back on the table then probed delicately with the end of a penknife.• While waiting he brought out a penknife and began whittling away a table-top.• Billy used his penknife to fashion a needle sharp point on each of the sticks.• I think Mum worried that I might run amok and stick my penknife straight into Katie.• His scars were tourist penknife doodles. 