DTZa small knife with blades that fold into the handle, usually carried in your pocket 折叠式小刀SYN jackknife →5see picture at 见图knife1
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.