「Horse」with「mouth and limited range」(丈) suggests GALLOPING but not an activity that the animal can continue for long periods.「Regular masturbation, erection in taut orifice」as it refers to the GALLOPING feet of a service provider whilst lying on her backside supine, or prone…working her leg(s) reminded folks of piloting a boat with a rudder and sculling with a single oar while standing in the stern. Oldest version uses right elements of「vulva, middle」and「crotch」(㕜) or「rod in orifice of crotch」as the history of humanity, and the historical record of one year as it referred to the emperor's or lord's recorded access and results with individual concubines, a task of the eunuchs for maintaining some semblance of proof of paternity as the history of his majesty's rod in orifice of crotch, among some other notations.
　「Feeling nothing with taut erection in orifice」will likely result in a change to a faster pace, more frenzied action in order to reach the desired climactic response, cause the participants to simply give up, or rearrange the insertion point.
　Without a doubt, the Irish also have knowledge of their own to pass along in these trying times:「Masturbation will not spread coronavirus, especially if you wash your hands (and any sex toys) with soap and water for at least 20 seconds before and after.」Nonetheless and regrettably, unlike in dynastic China, it must be undertaken alone to truly be a preventative countermeasure but still achieve the desired result with some degree of safety.
　 　[　https://www.sexualwellbeing.ie/sexual-health/sex-and-coronavirus/ 2020-03-31　]　
　The Dutch, too have the same solution—it seems masturbation has become mainstream in the media the world over due to the coronavirus (it has always been 'the main stream' in reality, albeit covertly for most folks):
　「'Don't have sex with your partner if they have been isolated because of (suspected) coronavirus infection,' the RVIM says. 'Sex with yourself or with others at a distance is possible (think of telling erotic stories, masturbating together).'」
　　[　https://www.theguardian.com/world/2020/may/15/dutch-official-advice-to-single-people-find-a-sex-buddy-for-lockdown-coronavirus 2020-05-16　]　
　Needless to point out perhaps, but Chinese shamans from antiquity hit upon the same solution as a pandemic preventative countermeasure, honed for ultimate client satisfaction by utilizing naked females with no-longer-integrated feet as masturbatory sex buddies available for short-term rental with erotic visualization of live prepubescent female genitalia engaging in autoerotic stimulation herself, as a solution to the same problem facing us now, but in pre-Internet days.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: to gallop; speedily; to proceed to; to pilot (ship, plane etc); to sail
Unihan extended: sail, drive, pilot; fast, quick
EDRDG: run fast