If we are using Merriam-Webster, there’s no question that Abram lied about Sarai1,2, committing a sin. However, we look to scripture to interpret scripture, not to secular, human things to interpret scripture. Searching scripture we can find a very similar case to Abram’s involving Samuel3. Here, God instructed Samuel to “lie” (according to Merriam-Webster) to Saul3. On God’s command, Samuel intentionally deceived Saul about his purpose for coming3.
We would have to weigh Abram’s (and Samuel’s) situation while remembering a couple of important attributes of God’s unchanging character. First, God is not a respecter of persons7, so for example, we couldn’t say He was somehow making an exception for Samuel3. Second, among the things that God cannot do is lie4,5,6 or associate with any sin8.
Therefore, we are forced to conclude that Abram did not “lie” about Sarai, as we might define lying. Maybe better said, Abram did not lie in a sinful way concerning Sarai.