Relegation-threatened Giants had been 12-10 down until that point and in danger of suffering another defeat that would leave them joint-bottom with just two games remaining.
But Senior’s finish before Matt Frawley rounded things off gave Huddersfield’s fight against the drop a massive boost.
“I just got a bit of space on the wing and just about got it down,” recalled the 19-year-old, who has begun to make his mark this term with Fiji international Akuila Uate missing much of the campaign.
“Their play got me up after it but I’d got the ball down first.
“I’d fluffed a try earlier when I went down the touchline and passed inside to one of their guys so I was just really relieved to get that one as I should have scored the first.
“It’s been a long time since we got a win and that one there gives us real confidence going into the last couple of games.
“I don’t think we’re home and dry yet in the relegation battle but it puts us in good stead and that was huge.
“We’ll keep an eye on those fixtures and we should be fine but I think we have another win in us.”
Hull would have gone second with a victory themselves but they struggled for ideas trying to break down Huddersfield’s spirited defence in the second half and Simon Woolford’s side earned their first win in four games.
Full-back Darnell McIntosh, the converted 22-year-old winger, came up with two try assists, finding the passes for Jermaine McGillvary’s opener and Senior’s score.
“I think that was one of the best games Darnell has played at full-back,” said Senior, who came through the Giants Academy like his colleague.
“I think he is a good full-back, is a real confidence player and played with plenty of that tonight.
“He was real good.”
Huddersfield head to League Leaders’ Shield winners St Helens on Friday before finishing off at home to Catalans Dragons.