After completing his service, he is considering reenlisting to continue his military career.

reenlisting 是动词 reenlist 的现在分词形式。reenlist 由前缀 re-（表示"再次"）和动词 enlist（"入伍、参军"）组成，字面意思是"再次入伍"，即"重新参军"。 在军事语境中，reenlist 特指军人服役期满后再次签订服役合同的行为。