A possible synonym for “define to” could be “characterize as”.
When we use “define to”, we are essentially giving a specific meaning or description to something. For example, “We define success to be achieving one's goals.” Here, we are specifying what success means.
Similarly, when we say “characterize as”, we are also describing or defining something. For instance, “He characterized the new policy as a bold step forward.” In this case, we are giving a particular characteristic or description to the policy.
Another possible synonym could be “label as”. For example, “They labeled the behavior as inappropriate.” This is similar to defining something by giving it a specific label or description.
“describe as” is also a good alternative. For example, “She described the experience as unforgettable.” This implies giving a description that is similar to defining something.