“使自乘二次”可以翻译为 “to raise to the second power (self-multiplied twice)” 或者更简洁地表达为 “to square (which implies multiplying a number by itself once, and here emphasizing the operation done twice conceptually in a broader sense, though in strict math terms squaring is multiplying by itself once; for precise 'multiplying by itself twice' it could be phrased as 'to raise to the fourth power' if starting from the base and multiplying by itself three additional times in total, but if the context is about a general step of multiplying by itself twice from some starting point, 'to perform two successive self-multiplications' could also work)” 。
不过在日常和大多数数学语境中，如果要表达一个数经过两次自身相乘的操作（比如从基数开始，先乘一次自己，再拿结果乘一次自己），较为准确且常见的表达可能会根据具体情境有所不同：
如果强调操作过程，可以说 “to perform two successive multiplications of the number by itself” 。
如果从最终幂次角度，若初始是基数1次幂，两次自乘后是基数的4次幂（因为 $x\times x\times x\times x=x^4$ ），可说 “to raise to the fourth power” （但要注意这种说法隐含了从基数1次幂开始进行两次自乘到达4次幂的逻辑，如果起始状态不是基数1次幂，这种说法就不准确了）。
最贴合“使自乘二次”字面且通用性较好的是 “to perform two successive self-multiplications” 。