[1] The headword is aorist indicative active of e)fi/sthmi (cf. epsilon 2623, epsilon 3933, epsilon 3934), third person singular. It is probably extracted from the quotation given, which does illustrate the relevant usage, though there is no nu-moveable in the headword itself.
2Quotation not identified by Adler, but TLG searching reveals it to be Cassius Dio 17.57.78 (contextless). (Could also mean "he suddenly stopped the race.")