Answer: Gestures, whether we consider them obscene or not, are one of the nonverbal ways humans communicate with the world around them. They include movements of the fingers, hands, arms or other parts meant to transmit a message. They run the gamut from those considered harmless (such as waving a hand to signal hello) to those considered obscene (gestures meant to put down, insult, or belittle someone else).
The Bible has quite a bit to say about various gestures people made in antiquity. While some of them were used for unacceptable (obscene or sinful) purposes, others were not only good but also encouraged.
Job, in defense of his integrity, lists several things he did not do because of his Godly fear. One of them was having his mouth kiss his hand (Job 31:14, 27 - 28). This obscene gesture (at least from God's point of view) was made, during the time of Job, to pay homage to false (pagan) gods (John Gill's Exposition).
King Solomon points out various gestures used by those who not only accuse others but also wish to carry out their perverse plans. He states, "A worthless person, a wicked man, walks with a perverse (obscene) mouth, winking with his eyes (a sign sometimes used in gambling), speaking with his feet, pointing with his fingers. . ." (Proverbs 6:12 - 14).
The prophet Ezekiel was shown the idolatrous practices of those who served in His temple. These religious leaders not only secretly worshipped the rising sun, they also "put the branch to their nose." Although Biblical commentaries vary regarding the exact meaning of this phrase, it was certainly a gesture of contempt and one which the Eternal thought was "obscene" (Ezekiel 8:16 - 17).
Scripture also denounces, through the prophet Isaiah, one of several common gestures known as the "pointing of the finger" (Isaiah 58:9). Psalm 22 is a prophecy regarding the verbal abuse and deriding (obscene gestures) Christ would experience as he suffered and died for our sins (Psalm 22:7 - 8, see also Matthew 27:39 - 43).
While some gestures are merely referenced (and not considered obscene) in the Bible, others are encouraged. For example, striking or joining hands was an ancient form of entering into an agreement or a treaty (Proverbs 6:1, 11:21).
Shaking a hand above one's head was a beckoning sign to gather people together (Isaiah 13:2). Ancient Israel's priests were commanded to wave a sheaf of newly harvested grain during the Spring Holy Days (Leviticus 23:9 - 11).
Lifting up hands while worshipping and praying to God was commonly practiced in the Old Testament (1Kings 8:22, Psalms 28:2, 63:4, 68:31, 141:2, Isaiah 1:15, etc.). This practice continued in the New Testament. The apostle Paul stated he desired believers to beseech our Creator with raised hands that are free from anger and contention (1Timothy 2:8).
In closing, the meaning of a particular gesture can vary depending on a variety of factors. What is considered benign in one place can be viewed as obscene in another. That said, any gestures meant to insult or convey an attitude of rejection (hatred, contempt, etc.) toward another person, according to the Bible, are not acceptable in the life of a Christian.