noun, na-adjective, noun which may take the genitive case particle 'no'
eventful at home and abroad; many things happening both inside and outside the country
A formal, somewhat literary expression used to describe a period when many significant events are occurring both domestically and internationally. Often used in news or political commentary.
内外多事の折、政府は慎重な対応を求められている。
At a time when many things are happening at home and abroad, the government is being asked to respond carefully.
今年は内外多事な一年だった。
This year was an eventful one both domestically and internationally.
多事 means 'eventful' or 'busy with many matters' in general, while 内外多事 specifically emphasizes that the events are occurring both domestically and internationally.
内憂外患 refers to troubles or worries both at home and from abroad, often with a negative connotation, whereas 内外多事 is more neutral and simply indicates a high level of activity.
Compound of 内外 (domestic and foreign) and 多事 (many events). The exact historical derivation is uncertain, but it follows a common Sino-Japanese pattern for formal expressions.